Cost of revenue, including related party, excluding amortization

754,169

493,083

309,332

Costs and expenses:

^[1],[2]

4,273

2,946

1,443

Selling and marketing

^[1]

674,729

461,219

286,234

Technology and content

^[1]

51,658

28,693

15,388

General and administrative, including related party shared service fee

^[1],[3]

54,097

18,065

6,536

Amortization of intangible assets

13,857

30,030

30,025

Operating income (loss)

(44,445)

(47,870)

(30,294)

Other income (expense)

Interest expense

(137)

(147)

(11)

Other, net

(139)

(2,667)

(1,435)

Total other income (expense), net

(276)

(2,814)

(1,446)

Income (loss) before income taxes

(44,721)

(50,684)

(31,740)

Expense (benefit) for income taxes

6,670

(11,318)

(8,644)

Net loss

(51,391)

(39,366)

(23,096)

Net loss attributable to noncontrolling interests

710

239

Net loss attributable to trivago N.V.

€ (50,681)

€ (39,127)

€ (23,096)

Earnings per share attributable to trivago N.V. available to common stockholders:

Basic and diluted (in EUR per share)

^[4]

€ 0.00

Shares used in computing earnings per share:

Weighted average shares of Class A and Class B common stock outstanding - basic and diluted

237,811

[1]	Includes share-based compensation as follows: Year ended December 31, 201420152016Cost of revenue—238737Selling and marketing1,0523,36010,913Technology and content, net of capitalized internal-use software and website development costs1,2074,54515,816General and administrative1235,98626,256
[2]	Year ended December 31, 201420152016Amortization of acquired technology included in Amortization of intangible assets is as follows:19,92719,9273,750Amortization of internal use software and website development costs included in Technology and content is as follows:1914751,410
[3]	Includes related party shared service fee as follows: Year ended December 31, 201420152016General and administrative1,5062,8264,185
[4]	Represents earnings per share of Class A and Class B common stock and weighted-average shares of Class A and Class B common stock outstanding for the period from December 16, 2016 through December 31, 2016, the period following the capitalization of the parent company and IPO (see Note 13).

Consolidated statements of operations (Parenthetical) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based compensation	€ 53,700	€ 14,100	€ 2,400
Amortization of intangible assets	13,857	30,030	30,025
General and administrative expenses from related party	4,185	2,826	1,506
Cost of revenue
Share-based compensation	737	238	0
Selling and marketing
Share-based compensation	10,913	3,360	1,052
Technology and content, net of capitalized internal-use software and website development costs
Share-based compensation	15,816	4,545	1,207
General and administrative
Share-based compensation	26,256	5,986	123
Acquired technology
Amortization of intangible assets	3,750	19,927	19,927
Internal use software and website development costs
Amortization of intangible assets	€ 1,410	€ 475	€ 191

Consolidated statements of comprehensive income (loss) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net loss	€ (51,391)	€ (39,366)	€ (23,096)
Other comprehensive income (loss)
Currency translation adjustments	161	(166)	0
Total other comprehensive income (loss)	161	(166)	0
Comprehensive loss	(51,230)	(39,532)	(23,096)
Less: Comprehensive loss attributable to noncontrolling interests	581	393	0
Comprehensive loss attributable to trivago N.V.	€ (50,649)	€ (39,139)	€ (23,096)

Consolidated balance sheets - EUR (€)	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash	€ 227,298,000	€ 17,556,000
Restricted cash	884,000	685,000
Accounts receivable, less allowance of €251 and €152 at December 31, 2015 and December 31, 2016, respectively	36,658,000	19,748,000
Accounts receivable, related party	16,505,000	23,605,000
Prepaid expenses and other current assets	11,529,000	4,603,000
Total current assets	292,874,000	66,197,000
Property and equipment, net	46,862,000	12,853,000
Other long-term assets	955,000	936,000
Intangible assets, net	176,052,000	189,909,000
Goodwill	490,503,000	490,360,000
TOTAL ASSETS	1,007,246,000	760,255,000
Current liabilities:
Accounts payable	39,965,000	26,263,000
Income taxes payable	3,433,000	256,000
Short-term debt	0	20,000,000
Members’ liability	0	13,377,000
Related party payable (Note 9 and 16)	0	7,129,000
Deferred revenue	5,078,000	2,264,000
Accrued expenses and other current liabilities	12,627,000	2,720,000
Total current liabilities	61,103,000	72,009,000
Deferred income taxes	53,156,000	57,994,000
Other long-term liabilities	38,565,000	5,896,000
Commitments and contingencies (Note 15)
Redeemable noncontrolling interests	351,000	2,076,000
Stockholders'/members' equity:
Subscribed capital	0	48,000
Reserves	584,667,000	695,871,000
Contribution from Parent	122,200,000	55,529,000
Accumulated other comprehensive income (loss)	21,000	(12,000)
Retained earnings (accumulated deficit)	(179,837,000)	(129,156,000)
Total stockholders' equity attributable to trivago N.V. / members' equity	654,258,000	622,280,000
Noncontrolling interest	199,813,000	0
Total stockholders' / members' equity	854,071,000	622,280,000
TOTAL LIABILITIES AND STOCKHOLDERS' / MEMBERS’ EQUITY	1,007,246,000	760,255,000
Class A Common Stock
Stockholders'/members' equity:
Common stock	1,802,000	0
Class B Common Stock
Stockholders'/members' equity:
Common stock	€ 125,405,000	€ 0

Consolidated balance sheets (Parenthetical) - EUR (€) € in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accounts receivable, allowance	€ 152	€ 251
Class A Common Stock
Class common stock, par value	€ 0.06
Class common stock, shared authorized	700,000,000
Class common stock, shares issued	30,026,635
Entity Common Stock, Shares Outstanding	30,026,635
Class B Common Stock
Class common stock, par value	€ 0.60
Class common stock, shared authorized	320,000,000
Class common stock, shares issued	209,008,088
Entity Common Stock, Shares Outstanding	209,008,088

Consolidated statements of changes in equity - EUR (€) € in Thousands	Total	Subscribed capital	Common Stock Class A Common Stock	Common Stock Class B Common Stock	Reserves	Retained earnings (accumulated deficit)	Accumulated other comprehensive income (loss)	Contribution from Parent	Noncontrolling interest
Beginning balance at Dec. 31, 2013	€ 684,407	€ 38			€ 700,105	€ (66,933)	€ 0	€ 51,197
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss), excluding portion attributable to redeemable noncontrolling interest	(23,096)					(23,096)
Other comprehensive loss (net of tax)	0
Contribution from Parent	1,506							1,506
Share-based compensation expense	1,751				1,751
Ending balance at Dec. 31, 2014	664,568	38			701,856	(90,029)	0	52,703
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss), excluding portion attributable to redeemable noncontrolling interest	(39,127)					(39,127)
Other comprehensive loss (net of tax)	(12)						(12)
Adjustment to the fair value of redeemable noncontrolling interests	(239)				(239)
Issue of subscribed capital, options granted	10	10
Contribution from Parent	2,826							2,826
Share-based compensation expense	(5,746)				(5,746)
Ending balance at Dec. 31, 2015	622,280	48			695,871	(129,156)	(12)	55,529	€ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive loss (net of tax)	33						33
Settlement of options exercised	4,930	1			4,929
Adjustment to the fair value of redeemable noncontrolling interests	(995)				(995)
Contribution from Parent	4,185							4,185
Corporate reorganization	0	(49)	€ 552	€ 125,405	(344,914)				219,006
Dividends to noncontrolling interest holder	(170)				(170)
Issuance of common stock	202,921		1,250		201,671
Changes in ownership of noncontrolling interests	0				19,478				(19,478)
Reclassification of option liability to reserves	4,893				4,893
Changes in ownership of redeemable noncontrolling interests	980				980
Ending balance at Dec. 31, 2016	€ 854,071	€ 0	€ 1,802	€ 125,405	€ 584,667	€ (179,837)	€ 21	€ 122,200	€ 199,813

Consolidated statements of changes in equity (Parenthetical) € in Thousands	12 Months Ended
	Dec. 31, 2016 EUR (€)
Statement of Stockholders' Equity [Abstract]
Issuance costs	€ 4,921
Net loss attributable to redeemable noncontrolling interest	€ 995

Consolidated statements of cash flows - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities:
Net loss	€ (51,391)	€ (39,366)	€ (23,096)
Adjustments to reconcile net loss to net cash used:
Depreciation (property and equipment and internal-use software and website development)	5,083	2,649	1,400
Amortization of intangible assets	13,857	30,030	30,025
Share-based compensation (See Note 9)	53,722	14,129	2,382
Deferred income taxes	(4,838)	(10,444)	(9,315)
Foreign exchange (gain) loss	(16)	960	1,554
Bad debt (recovery) expense	1,589	(410)	408
Non-cash charge, contribution from Parent	4,185	2,826	1,506
Changes in operating assets and liabilities, net of effects from of businesses acquired:
Accounts receivable, including related party	(11,256)	(18,540)	(10,710)
Prepaid expense and other assets	(7,144)	(121)	(461)
Accounts payable	13,879	13,102	6,930
Accrued expenses and other liabilities	7,486	2,415	(2,351)
Deferred revenue	2,814	1,780	485
Taxes payable/receivable, net	3,177	(25)	1,873
Net cash (used in) / provided by operating activities	31,147	(1,015)	630
Investing activities:
Acquisition of redeemable noncontrolling interests	(874)	0	0
Acquisition of business, net of cash acquired	0	(286)	(897)
Capital expenditures, including internal-use software and website development	(8,121)	(6,224)	(3,726)
Net cash used in investing activities	(8,995)	(6,510)	(4,623)
Financing activities:
Payments of initial public offering costs	(882)	0	0
Proceeds from issuance of credit facility	20,000	20,000	0
Payments on credit facility	(40,000)	0	0
Payment of loan to shareholder	0	(7,129)	0
Payment of loan to related party	0	(1,039)	0
Net proceeds from issuance of common stock	207,840	0	0
Proceeds from exercise of option awards	685	0	0
Proceeds from issuance of loan from related party	0	7,129	1,039
Proceeds from exercise of members’ equity awards	1	10	0
Net cash provided by financing activities	187,644	18,971	1,039
Effect of exchange rate changes on cash	(54)	(32)	105
Net increase (decrease) in cash	209,742	11,414	(2,849)
Cash at beginning of year	17,556	6,142	8,991
Cash at end of year	227,298	17,556	6,142
Supplemental cash flow information:
Cash paid for interest	160	100	11
Cash paid for taxes	8,696	751	2,100
Non-cash investing and financing activities:
Offering costs included in accrued expenses	4,038	0	0
Fixed assets-related payable	129	306	53
Capitalization of construction in process related to build-to-suit lease	30,883	4,852	0
Extinguishment of loan to members through contribution from Parent in members’ equity	7,129	0	0
Extinguishment of loan from related party through members’ liability	€ 7,129	€ 0	€ 0

Organization and basis of presentation	12 Months Ended
Organization and basis of presentation	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and basis of presentation	Organization and basis of presentation Description of business trivago N.V., (“trivago” the “Company,” “us,” “we” and “our”) and its subsidiaries offer online meta-search for hotels by facilitating consumers’ search for hotel accommodation, through online travel agents (“OTAs”), hotel chains and independent hotels. Our search-driven marketplace, delivered on websites and apps, provides users with a tailored search experience via our proprietary matching algorithms. We employ a ‘cost-per-click’ (or “CPC”) pricing structure, allowing advertisers to control their own return on investment and the volume of lead traffic we generate for them. During 2013, Expedia, Inc. (the "Parent" or "Expedia") completed the purchase of a controlling interest in the Company. Initial public offering In December 2016, we sold 20,826,606 ADSs, each representing one Class A share, with a nominal value of €0.06 per share, in our initial public offering (“IPO”) at a public offering price of $11.00 per ADS, for aggregate net offering proceeds to us, after deducting underwriting discounts and commissions, of €207.8 million. Corporate reorganization In connection with the IPO, the Company underwent a corporate reorganization, and as of December 31, 2016, trivago N.V. is the parent holding company with a 68.3% controlling interest in trivago GmbH. Prior to the completion of the IPO, Expedia owned 63.5% and Messrs. Schrömgens, Vinnemeier and Siewert, (whom we collectively refer to as the “Founders”) owned 36.5%, in aggregate, of the voting power in trivago GmbH. On November 7, 2016, travel B.V., a Dutch private company with limited liability under Dutch law was formed in order to affect the corporate reorganization. Prior to the completion of the IPO, Expedia contributed all of its shares in trivago GmbH to travel B.V. in a capital increase in exchange for newly issued Class B shares of travel B.V. The Founders contributed 940 shares of trivago GmbH, representing 6.7% of their aggregate shareholding in trivago GmbH, to travel B.V. in a capital increase in exchange for newly issued Class A shares of travel B.V. As a result of these contributions, 96.3% of the share capital and 99.6% of the voting power in travel B.V. was held by Expedia and 3.7% of the share capital and 0.4% of the voting power in travel B.V. was held by the Founders, whereas 66.0% of the voting power in trivago GmbH was held by travel B.V. and 34.0% of the voting power in trivago GmbH was held by the Founders. Effective with the IPO, travel B.V., changed its legal form and became trivago N.V and all Class A and B shares of travel B.V. were converted to Class A and B shares of trivago N.V. ADSs representing the 9,200,029 Class A shares of the Founders in trivago N.V. and additional 20,826,606 ADSs representing newly issued Class A shares in trivago N.V. were sold in the IPO. After the IPO, 68.3% of the voting power in trivago GmbH is held by trivago N.V. and 31.7% is held by the Founders which is reflected as noncontrolling interest in these consolidated financial statements. As of December 31, 2016, Expedia’s ownership interest and voting interest in trivago N.V. was 87.4% and 98.6%, respectively. Assuming the share capital increase of trivago GmbH that became effective on February 8, 2017 had been effective at that time, Expedia’s indirect ownership interest and voting interest in trivago GmbH was 59.7% and 64.7%, respectively. Basis of presentation The corporate reorganization, as described above, is considered a transaction between entities under common control. As a result, the financial statements for periods prior to the IPO and the corporate reorganization are the financial statements of trivago GmbH as the predecessor to the Company for accounting and reporting purposes. Unless otherwise specified, “the Company” refers to trivago N.V., and trivago GmbH and its respective subsidiaries throughout the remainder of these notes. These consolidated financial statements reflect Expedia’s basis of accounting due to the change in control in 2013 when Expedia acquired a controlling ownership in trivago, as we elected the option to apply pushdown accounting in the period in which the change in control event occurred. Expedia incurs certain costs on behalf of trivago. The consolidated financial statements reflect the allocation of certain of Expedia’s corporate expenses to trivago (see Note 16 - Related Parties for further information). We recorded all corporate allocation charges from Expedia within our consolidated statement of operations and as a contribution from Parent within the consolidated statement of changes in equity. Our management believes that the assumptions underlying the consolidated financial statements are reasonable. However, this financial information does not necessarily reflect the future financial position, results of operations and cash flows of trivago, nor does it reflect what the historical financial position, results of operations and cash flows of trivago would have been had we been a stand-alone company during the periods presented. Seasonality We experience seasonal fluctuations in the demand for our services as a result of seasonal patterns in travel. For example, our revenue is generally highest in the second and third quarters of each year. Our revenue typically decreases in the fourth quarter. We generally expect to experience higher profits in the second half of the year as we typically have higher marketing expenses in the first half of the year in advance of high travel seasons. Seasonal fluctuations affecting our revenue also affect the timing of our cash flows. We typically receive payment for referrals within 30 days of the referral. Therefore, our cash flow varies seasonally with a slight lag to our revenue, and is significantly affected by the timing of our advertising spending. The continued growth of our offerings in countries and areas where seasonal travel patterns vary may influence the typical trend of our seasonal patterns in the future.

Significant accounting policies	12 Months Ended
Significant accounting policies	Dec. 31, 2016
Accounting Policies [Abstract]
Significant accounting policies	Significant accounting policies Consolidation Our consolidated financial statements include the accounts of trivago and entities we control. All significant intercompany balances and transactions have been eliminated in consolidation. We record noncontrolling interest in our consolidated financial statements to recognize the minority ownership interest in our consolidated subsidiaries. Noncontrolling interest in the earnings and losses of consolidated subsidiaries represent the share of net income or loss allocated to members or partners in our consolidated entities, which includes the noncontrolling interest share of net income or loss from our redeemable noncontrolling interest entities and our noncontrolling interest in trivago GmbH. As discussed in Note 1, as a result of the corporate reorganization, trivago N.V. consolidates trivago GmbH and trivago GmbH is considered to be the predecessor to trivago N.V. for accounting and reporting purposes. We characterize the 31.7% minority interest in trivago GmbH as of December 31, 2016 as a noncontrolling interest and classify it as a component of stockholders’ equity in our consolidated financial statements. Noncontrolling interests with shares redeemable at the option of the minority holders in myhotelshop and base7 have been included in redeemable noncontrolling interests. We classify the redeemable noncontrolling interest as a mezzanine equity below non-current liabilities in our consolidated financial statements. See Note 11 - Redeemable noncontrolling interests for further discussion. Accounting estimates We use estimates and assumptions in the preparation of our consolidated financial statements in accordance with accounting principles generally accepted in the United States (“GAAP”). Our estimates and assumptions affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of our consolidated financial statements. These estimates and assumptions also affect the reported amount of net income or loss during any period. Our actual financial results could differ significantly from these estimates. The significant estimates underlying our consolidated financial statements include revenue recognition, intangible assets and goodwill, redeemable noncontrolling interest, acquisition purchase price allocations, and share-based compensation. Revenue recognition We recognize revenue from services rendered when the following four revenue recognition criteria are met: persuasive evidence of an arrangement exists, services have been rendered, the price is fixed or determinable, and collectability is reasonably assured. Revenue is generated each time a visitor to one of our websites or apps clicks on a hotel room offer in our search results and is referred to one of our advertisers. Advertisers pay on a per referral basis, with the aforementioned visitor click-through being considered a single referral. Given the nature of the industry, it is not unusual for referrals to be generated from automated scripts designed to browse and collect data on our websites. However, review processes are in place to identify anomalies to ensure revenue recognition is appropriate. Pricing is determined through a competitive bidding process whereby advertisers bid on their placement priority for a specific room offer within each room listing. Bids can be placed as often as daily, and changes in bids are applied on a prospective basis on the following day. Additionally, a portion of our revenue is generated through subscription-based services earned through trivago Hotel Manager Pro applications. This revenue is recognized ratably over the subscription period with deferred revenue recognized upon receipt of payment in advance of revenue recognition. Cost of revenue Cost of revenue consists of expenses that are directly or closely correlated to revenue generation, including data center costs, salaries and share-based compensation for our data center operations staff and our customer service team who are directly involved in revenue generation. For the three years ended December 31, 2014, 2015 and 2016 cost of revenue excludes €19.9 million, €19.9 million and €3.8 million, respectively, of amortization expense of acquired technology. As of December 31, 2014, 2015 and 2016 cost of revenue excludes €0.2 million, €0.5 million and €1.4 million, respectively, of amortization expense related to internal use software and website development. Restricted cash Restricted cash primarily consists of funds held as guarantees in connection with corporate leases and funds held in escrow accounts in the event of default on corporate credit card statements. The carrying value of restricted cash approximates its fair value. Accounts receivable Accounts receivable are generally due within thirty days and are recorded net of an allowance for doubtful accounts. We determine our allowance by considering a number of factors, including the length of time trade accounts receivable are past due, previous loss history, a specific customer’s ability to pay its obligations to us, and the condition of the general economy and industry as a whole. Property and equipment, net including software and website capitalization We record property and equipment at cost, net of accumulated depreciation and amortization. We compute depreciation using the straight-line method over the estimated useful lives of the assets, which is generally three to five years for computer equipment, capitalized software development and furniture and other equipment. We amortize leasehold improvement using the straight-line method, over the shorter of the estimated useful life of the improvement or the remaining term of the lease, the majority of which will be fully amortized through 2018. Certain direct development costs associated with website and internal-use software are capitalized during the application development stage. Capitalized costs include external direct costs of services and payroll costs (including share-based compensation). The payroll costs are for employees devoting time to the software development projects principally related to website and mobile app development, including support systems, software coding, designing system interfaces and installation and testing of the software. These costs are recorded as property and equipment and are generally amortized over a period of three years beginning when the asset is ready for use. Costs incurred for enhancements that are expected to result in additional features or functionality are capitalized and amortized over the estimated useful life of the enhancements, which is generally a period of three years. Costs incurred during the preliminary project stage, as well as maintenance and training costs, are expensed as incurred. Leases We lease office space in several countries under non-cancelable lease agreements. We generally lease our office facilities under operating lease agreements. We recognize rent expense on a straight-line basis over the lease period. Any lease incentives are recognized as reductions of rental expense on a straight-line basis over the term of the lease. The lease term begins on the date we become legally obligated for the rent payments or when we take possession of the office space, whichever is earlier. We establish assets and liabilities for the estimated construction costs incurred under lease arrangements where we are considered the owner for accounting purposes only, or build-to-suit leases, to the extent that we are involved in the construction of structural improvements or take construction risk prior to commencement of a lease. In July 2015, we entered into a lease for new corporate headquarters with 26,107 square meters of office space. Pursuant to the lease, the Landlord will build this office building in Düsseldorf, Germany. As a result of our involvement in the construction project and our responsibility for paying a portion of the costs of normal finish work and structural elements of the premises, the Company was deemed for accounting purposes to be the owner of the premises during the construction period pursuant to build-to-suit lease accounting guidance under ASC 840. Therefore, the Company recorded project construction costs during the construction period incurred by the landlord as a construction-in-progress asset and a related construction financing obligation on our consolidated balance sheets. The amounts that the Company has paid or incurred for normal tenant improvements and structural improvements had also been recorded as part of the construction-in-progress asset. We have a lease that includes both building and land. We have bifurcated our lease payments pursuant to the premises into: a portion that is allocated to the building (a reduction to the financing obligation); and a portion that is allocated to the land on which the building was constructed. The portion of the lease obligations allocated to the land is treated as an operating lease that commenced in July 2015. For the years ended December 31, 2015 and 2016, we have recorded €0.9 million and €1.7 million, respectively, of land rent expense in connection with this lease. Business combinations We assign the value of the consideration transferred to acquire a business to the tangible assets and identifiable intangible assets acquired and liabilities assumed on the basis of their fair values at the date of acquisition. Any excess purchase price over the fair value of the net tangible and intangible assets acquired is allocated to goodwill. When determining the fair values of assets acquired and liabilities assumed, management makes significant estimates and assumptions, especially with respect to intangible assets. Critical estimates in valuing certain intangible assets include but are not limited to future expected cash flows from customer relationships and discount rates. Management’s estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates. Recoverability of goodwill and indefinite-lived intangible assets Goodwill is assigned to our three reporting units, which correspond to our three operating segments, on the basis of their relative fair values as of the date of change in reporting units. We assess goodwill and indefinite-lived assets, neither of which are amortized, for impairment annually in the fourth quarter of the year, or more frequently, if events and circumstances indicate that an impairment may have occurred. In the evaluation of goodwill for impairment, we typically first perform a qualitative assessment to determine whether it is more likely than not that the fair value of each reporting unit is less than its carrying amount. If so, we perform a quantitative assessment and compare the fair value of that reporting unit to its carrying value. If the carrying value of a reporting unit exceeds its fair value, the goodwill of that reporting unit is potentially impaired and we proceed to step two of the impairment analysis. In step two of the analysis, we will record an impairment loss equal to the excess of the carrying value of the reporting unit’s goodwill over its implied fair value should such a circumstance arise. Periodically, we may choose to forgo the initial qualitative assessment and perform quantitative analysis to assist in our annual evaluation. We generally base the measurement of fair value of our three reporting units on a blended analysis of the present value of future discounted cash flows and market valuation approach. The discounted cash flows model indicates the fair value of the reporting unit based on the present value of the cash flows that we expect the reporting unit to generate in the future. Our significant estimates in the discounted cash flows model include our weighted average cost of capital, long-term rate of growth and profitability of our business. The market valuation approach indicates the fair value of the business based on a comparison of the reporting unit to comparable publicly traded firms in similar lines of business. Our significant estimates in the market approach model include identifying similar companies with comparable business factors, such as size, growth, profitability, risk and return on investment and assessing comparable revenue and operating income multiples in estimating the fair value of the reporting unit. We believe the weighted use of discounted cash flows and market approach is the best method for determining the fair value of our reporting units because these are the most common valuation methodologies used within the travel and Internet industries; and the blended use of both models compensates for the inherent risks associated with either model if used on a stand-alone basis. In addition to measuring the fair value of our reporting units as described above, we consider the combined carrying and fair values of our reporting units in relation to the company’s total fair value. In our evaluation of our indefinite-lived intangible assets, we typically first perform a qualitative assessment to determine whether the fair value of the indefinite-lived intangible assets is more likely than not impaired. If so, we perform a quantitative assessment and an impairment charge is recorded for the excess of the carrying value of the indefinite-lived intangible assets over the fair value. We base our measurement of the fair value of our indefinite-lived intangible assets, which consist of trade name, trademarks, and domain names using the relief-from-royalty method. This method assumes that the trade name and trademarks have value to the extent that their owner is relieved of the obligation to pay royalties for the benefits received from them. As with goodwill, periodically, we may choose to forgo the initial qualitative assessment and perform a quantitative analysis in our annual evaluation of indefinite-lived intangible assets. Recoverability of intangible assets with definite lives and other long-lived assets Intangible assets with definite lives and other long-lived assets are carried at cost and are amortized on a straight-line basis over their estimated useful lives of generally less than seven years. We review the carrying value of long-lived assets or asset groups, including property and equipment whenever events or changes in circumstances indicate that the carrying amount of the assets might not be recoverable. Factors that would necessitate an impairment assessment include a significant adverse change in the extent or manner in which an asset is used, a significant adverse change in legal factors or the business climate that could affect the value of the asset, or a significant decline in the observable market value of an asset, among others. If such facts indicate a potential impairment, we would assess the recoverability of an asset group by determining if the carrying value of the asset group exceeds the sum of the projected undiscounted cash flows expected to result from the use and eventual disposition of the assets over the remaining economic life of the primary asset in the asset group. If the recoverability test indicates that the carrying value of the asset group is not recoverable, we will estimate the fair value of the asset group using appropriate valuation methodologies, which would typically include an estimate of discounted cash flows. Any impairment would be measured as the difference between the asset group’s carrying amount and its estimated fair value. Income taxes We record income taxes under the liability method. Deferred tax assets and liabilities reflect our estimation of the future tax consequences of temporary differences between the carrying amounts of assets and liabilities for book and tax purposes. We determine deferred income taxes based on the differences in accounting methods and timing between financial statement and income tax reporting. Accordingly, we determine the deferred tax asset or liability for each temporary difference based on the enacted tax rates expected to be in effect when we realize the underlying items of income and expense. We consider many factors when assessing the likelihood of future realization of our deferred tax assets, including our recent earnings experience by jurisdiction, expectations of future taxable income, and the carryforward periods available to us for tax reporting purposes, as well as other relevant factors. We may establish a valuation allowance to reduce deferred tax assets to the amount we believe is more likely than not to be realized. Due to inherent complexities arising from the nature of our businesses, future changes in income tax law, tax sharing agreements or variances between our actual and anticipated results of operations, we make certain judgments and estimates. Therefore, actual income taxes could materially vary from these estimates. We account for uncertain tax positions based on a two-step process of evaluating recognition and measurement criteria. The first step assesses whether the tax position is more likely than not to be sustained upon examination by the tax authority, including resolution of any appeals or litigation, based on the technical merits of the position. If the tax position meets the more likely than not criteria, the portion of the tax benefit greater than 50% likely to be realized upon settlement with the tax authority is recognized in the financial statements. Interest and penalties related to uncertain tax positions are classified in the financial statements as a component of income tax expense. Presentation of taxes in the statements of operations We present taxes that we collect from advertisers and remit to government authorities on a net basis in our consolidated statements of operations. Foreign currency translation and transaction gains and losses The consolidated Financial Statements have been prepared in euros, the reporting currency. Certain of our operations outside of the Eurozone use the local currency as their functional currency. We translate revenue and expense at average exchange rates during the period and assets and liabilities at the exchange rates as of the consolidated balance sheet dates and include such foreign currency translation gains and losses as a component of other comprehensive income. Due to the nature of our operations and our corporate structure, we also have subsidiaries that have significant transactions in foreign currencies other than their functional currency. We record transaction gains and losses in our consolidated statements of operations related to the recurring remeasurement and settlement of such transactions. Advertising expense We incur advertising expense consisting of offline costs, including television and radio advertising, as well as online advertising expense to promote our brands. A significant portion of traffic from users is directed to our websites through our participation in display advertising campaigns on search engines, advertising networks, affiliate websites and social networking sites. We consider traffic acquisition costs to be indirect advertising fees. We expense the production costs associated with advertisements in the period in which the advertisement first takes place. We expense the costs of communicating the advertisement (e.g., television airtime) as incurred each time the advertisement is shown. These costs are included in selling and marketing expense in our consolidated statements of operations. For the years ended December 31, 2014, 2015 and 2016, our advertising expense was €271.4 million, €432.2 million and €623.5 million, respectively. As of December 31, 2014, 2015 and 2016, we had €4.5 million, €3.8 million and €3.4 million, respectively, of prepaid marketing expenses included in prepaid expenses and other current assets. Share-based compensation All share-based compensation included in our consolidated financial statements relates to certain outstanding trivago employee options replaced with new trivago employee option awards exercisable into trivago Class A shares, in connection with the controlling-interest acquisition of trivago by Expedia in 2013. There were no options granted subsequent to the IPO through the end of the year. The following methods were used to measure the fair value of these awards prior to the IPO and we will continue to amortize the fair value thereof as follows for all pre-IPO equity grants: We measure the fair value of share options as of the grant date if equity treatment is applied, using the Black-Scholes option pricing model. The valuation model incorporates various assumptions including expected volatility of equity, expected term and risk-free interest rates. As we do not have a trading history for our Class A shares prior to the IPO, the expected share price volatility for our Class A shares prior to the IPO was estimated by taking the average historic price volatility for industry peers based on daily price observations over a period commensurate to the expected term. We base our expected term assumptions on the terms and conditions of the employee share option agreements, and scheduled exercise windows. Prior to the IPO, the share price assumption used in the model is based upon a valuation of trivago’s shares as of the grant date utilizing a blended analysis of the present value of future discounted cash flows and a market valuation approach. We amortize the fair value to the extent the awards qualify for equity treatment, over the vesting term on a straight-line basis. The majority of our share options vest between one and three years and have contractual terms that align with prescribed liquidation windows. We classify certain employee option awards as liabilities when we deem it not probable that the employees holding the awards will bear the risk and rewards of stock ownership for a reasonable period of time. We remeasure these instruments at fair value at the end of each reporting period using a Black-Scholes option pricing model which relies upon an estimate of the fair value of trivago’s shares as of the reporting date which is determined using a blended approach as discussed above. Upon settlement of these awards, our total share-based compensation expense recorded from grant date to settlement date will equal the settlement amount. We recognize the effect of forfeitures in the period that the award was forfeited. Fair value recognition, measurement and disclosure The carrying amounts of cash and restricted cash reported on our consolidated balance sheets approximate fair value as we maintain them with various high-quality financial institutions. The accounts receivable are short-term in nature and are generally settled shortly after the sale. We disclose the fair value of our financial instruments based on the fair value hierarchy using the following three categories: Level 1 - Valuations based on quoted prices for identical assets and liabilities in active markets. Level 2 - Valuations based on observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets and liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data. Level 3 - Valuations based on unobservable inputs reflecting the Company’s own assumptions, consistent with reasonably available assumptions made by other market participants. These valuations require significant judgment. Certain risks and concentration of credit risk Our business is subject to certain risks and concentrations including dependence on relationships with advertisers, dependence on third-party technology providers, and exposure to risks associated with online commerce security. Our concentration of credit risk relates to depositors holding the Company's cash and customers with significant accounts receivable balances. Our customer base includes primarily online travel agencies and hoteliers. We perform ongoing credit evaluations of our customers and maintain allowances for potential credit losses. We generally do not require collateral or other security from our customers. Expedia, our controlling shareholder, and its affiliates represent 32%, 39% and 36%, respectively, of our revenue for the years ended December 31, 2014, 2015 and 2016, and 55% and 31%, respectively, of total accounts receivable as of December 31, 2015 and 2016. Priceline.com and its affiliates represent 28%, 27% and 43%, respectively, of revenues for the years ended December 31, 2014, 2015 and 2016 and 21% and 48%, respectively, of total accounts receivable as of December 31, 2015 and 2016. Contingent liabilities We have no material legal matters as of December 31, 2015 or 2016, as discussed further in Note 15 - Commitments and Contingencies. Periodically, we review the status of all significant outstanding matters to assess the potential financial exposure. When (i) it is probable that an asset has been impaired or a liability has been incurred and (ii) the amount of the loss can be reasonably estimated, we record the estimated loss in our consolidated statements of operations. We provide disclosure in the notes to the consolidated financial statements for loss contingencies that do not meet both of these conditions if there is a reasonable possibility that a loss may have been incurred that would be material to the financial statements. Significant judgment is required to determine the probability that a liability has been incurred and whether such liability is reasonably estimable. We base accruals made on the best information available at the time, which can be highly subjective. The final outcome of these matters could vary significantly from the amounts included in the accompanying consolidated financial statements. See Note 15 - Commitments and Contingencies. Adoption of new accounting pronouncements In March 2016, the FASB issued new guidance related to accounting for share-based payments. The updated guidance changes how companies account for certain aspects of share-based payments awards to employees, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. The guidance is effective for annual and interim reporting periods beginning after December 15, 2016, with early adoption permitted. The adoption of this new guidance did not have a material impact to our consolidated financial statements. Recent accounting policies not yet adopted In May 2014, the FASB issued an ASU amending revenue recognition guidance and requiring more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. In August 2015, the FASB issued an ASU deferring the effective date of the revenue standard so it would be effective for annual and interim reporting periods beginning after December 15, 2017, with early adoption prohibited for accounting periods beginning before December 15, 2016. We expect to have our preliminary evaluation, including the selection of an adoption method, completed by the end of the first half of 2017. We are not planning on early adopting and currently expect to adopt the new revenue recognition guidance in the first quarter of 2018. In January 2016, the FASB issued new guidance related to accounting for equity investments, financial liabilities under the fair value option, and the presentation and disclosure requirements for financial instruments. In addition, the FASB clarified guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities. The new standard is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017. We are in the process of evaluating the impact of adopting this new guidance on our consolidated financial statements. In February 2016, the FASB issued new guidance related to accounting and reporting guidelines for leasing arrangements. The new guidance requires entities that lease assets to recognize assets and liabilities on the balance sheet related to the rights and obligations created by those leases regardless of whether they are classified as finance or operating leases. Consistent with current guidance, the recognition, measurement, and presentation of expenses and cash flows arising from a lease primarily will depend on its classification as a finance or operating lease. The guidance also requires new disclosures to help financial statement users better understand the amount, timing and uncertainty of cash flows arising from leases. This guidance is effective for annual and interim reporting periods beginning after December 15, 2018. Early adoption is permitted and should be applied using a modified retrospective approach. We are in the process of evaluating the impact of adopting this new guidance on our consolidated financial statements. In August and November 2016, the FASB issued new guidance related to the statement of cash flows which clarifies how companies present and classify certain cash receipts and cash payments as well as amends current guidance to address the classification and presentation of changes in restricted cash in the statement of cash flows. The new guidance is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017 with early adoption permitted. We are in the process of evaluating the impact of adopting this new guidance on our consolidated financial statements. In January 2017, the FASB issued new guidance clarifying the definition of a business for determining whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The new standard is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017 with early adoption permitted for transactions that occurred before the issuance date or effective date of the standard if the transactions were not reported in financial statements that have been issued or made available for issuance. We are in the process of evaluating the impact of adopting this new guidance on our consolidated financial statements. In January 2017, the FASB issued new guidance simplifying subsequent goodwill measurement by eliminating Step 2 from the goodwill impairment test. Under this update, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. The new standard is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2019 with early adoption permitted for annual goodwill impairment tests performed after January 1, 2017. The standard must be applied prospectively. We are in the process of evaluating the impact of adopting this new guidance on our consolidated financial statements.

Acquisitions

12 Months Ended

Dec. 31, 2016

Business Combinations [Abstract]

Acquisitions

On December 19, 2014, we completed the acquisition of a 100% equity interest in Rheinfabrik, for a total purchase consideration of €1.0 million in cash. The acquisition provides us a talent base of employees skilled in the Android and iOS app development.

On July 16, 2015, we completed the acquisition of a 61.3% equity interest in myhotelshop N.V. (“myhotelshop”), a marketing manager, for total purchase consideration of €0.6 million consisting of cash and the settlement of pre-existing debt at the closing of the acquisition. The acquisition provides trivago direct relationships with independent hotels through the myhotelshop portal.

On August 5, 2015, we completed the acquisition of a 52.3% equity interest in base7booking.com Sarl (“base7”), a cloud based property management service provider, for total purchase consideration of €2.1 million in cash. The acquisition provides us access to the Company’s workforce and the “know-how” regarding base7’s all-in-one property management system, which creates opportunity to enhance trivago’s direct marketing.

The acquisitions of base7 and myhotelshop provide us the opportunity to enhance our strategic marketing capabilities as we intend to integrate the workforce and independent hotel relationships acquired with ours in order to deliver an overall better customer experience to our customer base.

The purchase price from our acquisitions was allocated to the fair value of assets acquired and liabilities assumed in the respective years as follows:



	Year ended December 31,
(in thousands)	2014			2015
Goodwill		€	859		€	2,583
Identifiable intangible assets:
Customer relationships		0			38
Net assets acquired⁽¹⁾		180			2,224
Redeemable noncontrolling interest		0			(2,230		)
Total purchase consideration		€	1,039		€	2,615

⁽¹⁾ Includes cash acquired of €0.1 million and €2.4 million in 2014 and 2015, respectively.

The identifiable intangible asset relates to the customer relationships acquired as part of the myhotelshop acquisition. The fair value was estimated using the multi-period-excess-earnings method of the income approach (“Level 3” on the fair value hierarchy). Under this method, an intangible asset’s fair value is equal to the present value of the after-tax cash flows (excess earnings) attributable solely to the intangible asset over its remaining useful life. To calculate fair value, we estimated the present value of cash flows discounted at rates commensurate with the inherent risks associated with each type of asset. We believe that the level and timing of cash flows appropriately reflect market participant assumptions.

The goodwill of €0.9 million and €2.6 million for acquisitions in the years ended December 31, 2014 and 2015, respectively, is primarily attributable to assembled workforce and operating synergies. The goodwill has been allocated to our three operating segments and is not expected to be deductible for tax purposes.

The fair value of the noncontrolling interest in myhotelshop and base7 was estimated to be €2.2 million at the time of acquisition. In addition, the purchase agreement of myhotelshop and base7 each contain certain put/call rights whereby we may acquire, and the minority shareholders may sell to us, the minority shares of the company at fair value beginning in 2018 or earlier if the call option held by trivago is exercised to purchase the outstanding equity interest of base7. As the noncontrolling interest is redeemable at the option of the minority holders, we classified the balance as redeemable noncontrolling interest with future changes in the fair value above the initial basis recorded as charges or credits to retained earnings (or additional paid-in capital in absence of retained earnings).

Acquisition-related costs of €0.2 million and €0.8 million have been recognized in the statement of operations as general and administrative expenses for the years ended December 31, 2014 and 2015, respectively.

The acquired companies have been consolidated into our financial statements on the acquisition date. Revenue and operating loss recognized in 2014 for Rheinfabrik is not significant. We have recognized €1.4 million in revenue and €0.5 million in operating losses for the year ended December 31, 2015 for base7 and myhotelshop.

Combined Pro forma Information

Supplemental information on an unaudited combined pro forma basis, as if the acquisitions had been consummated on January 1, 2014, is presented as follows:



	Year ended December 31,
(in thousands)	2014				2015
Revenue		€	311,076			€	494,387
Net loss		€	(22,973	)		€	(39,359	)

On December 22, 2016, we exercised our call option in order to purchase the remaining 47.7% noncontrolling interest in base7 for a cash consideration of approximately €0.9 million. As such, we became the sole owner of base7. Given we had a controlling interest in base7 prior to the exercise of the call option, the change in ownership is treated as a step-acquisition and accounted for as an equity transaction. As such, we have eliminated the redeemable noncontrolling interest of base7 and changes in redeemable noncontrolling interest due to attributed earnings and foreign exchange gains/losses as of December 22, 2016 and any difference between carrying value and acquisition value was adjusted to Reserves in shareholders’ equity. See Note 11 - Redeemable noncontrolling interest.

Fair value measurement

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Fair value measurement

The redeemable noncontrolling interest is measured at fair value on a recurring basis as of December 31, 2015 and 2016 and classified using the fair value hierarchy in the tables below:



		December 31, 2015
(in thousands)	Total			Level 1			Level 2			Level 3
Redeemable noncontrolling interest:
Put/call option		€	2,076		€	0		€	0		€	2,076
Total mezzanine equity		€	2,076		€	0		€	0		€	2,076



	December 31, 2016
(in thousands)	Total			Level 1			Level 2			Level 3
Redeemable noncontrolling interest:
Put/call option		€	351		€	0		€	0		€	351
Total mezzanine equity		€	351		€	0		€	0		€	351

See Note 11 - Redeemable noncontrolling interest for further information on the fair value of the put/call option classified as Level 3. As of December 31, 2015, the carrying value of our credit facility approximates fair value, and the balance was zero as of December 31, 2016. For the years ended December 31, 2015 and 2016 we had no financial assets classified as Level 2 or 3. See Note 2 - Significant accounting policies for more information.

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

Property, Plant and Equipment [Abstract]

Property and equipment, net

12 Months Ended

Dec. 31, 2016

Property and equipment, net



	As of December 31,
(in thousands)	2015			2016
Capitalized software and software development costs		€	4,517	€	7,302
Computer equipment		5,186		8,358
Furniture and fixtures		1,963		2,743
Office equipment		394		1,009
Leasehold improvements		964		1,811
Subtotal		13,024		21,223
Less: accumulated depreciation		5,024		10,096
Construction in process		4,853		35,735
Property and equipment, net		€	12,853	€	46,862

As of December 31, 2015 and 2016, our internally developed capitalized software development costs, net of accumulated amortization, were €1.9 million and €2.6 million, respectively. For the years ended December 31, 2014, 2015 and 2016 we recorded amortization of capitalized software development costs of €0.2 million, €0.5 million, and €1.2 million, respectively, which is included in technology and content expenses within the consolidated statements of operations.

In June 2015, we signed a contract to build our new future corporate headquarters in Düsseldorf, Germany. The Company was deemed to be the owner of the premises during the construction period under build-to-suit lease accounting guidance under ASC 840. Therefore, a construction-in-progress asset and a related construction financing obligation were recorded on our consolidated balance sheets. The building assets are included in construction in process and will begin depreciating when the costs incurred related to the build out of the headquarters are complete and the normal tenant improvements are ready for their intended use, which is expected to be in 2018.

Goodwill and intangible assets, net

12 Months Ended

Dec. 31, 2016

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and intangible assets, net

The following table presents our goodwill and intangible assets as of December 31, 2015 and 2016:



	As of December 31,
(in thousands)		2015			2016
Goodwill			€	490,360		€	490,503
Intangible assets with definite lives, net			20,409			6,552
Intangible assets with indefinite lives			169,500			169,500
Total			€	680,269		€	666,555

Impairment Assessments

As of December 31, 2015 and 2016, we had no accumulated impairment losses of goodwill or indefinite-lived intangible assets.

Goodwill

The following table presents the changes in goodwill by reporting segment:



(in thousands)	Developed Europe				Americas				Rest of World				Total
Balance as of January 1, 2015		€	214,152			€	191,718			€	82,084			€	487,954
Additions		1,134				1,015				434				2,583
Foreign exchange translation		(78		)		(70		)		(29		)		(177		)
Balance as of December 31, 2015		215,208				192,663				82,489				490,360
Foreign exchange translation		63				56				24				143
Balance as of December 31, 2016		€	215,271			€	192,719			€	82,513			€	490,503

For the year ended December 31, 2015, the additions to goodwill relate to our acquisitions as described in Note 3 - Acquisitions.

Indefinite-lived Intangible Assets

Our indefinite-lived intangible assets relate principally to trade names, trademarks and domain names.

Intangible Assets with Definite Lives

The following table presents the components of our intangible assets with definite lives as of December 31, 2015 and 2016:



(in thousands)		December 31, 2015									December 31, 2016
	Cost			(Accumulated Amortization)				Net			Cost			(Accumulated Amortization)				Net
Customer relationships		€	38		€	(5	)		€	33		€	38		€	(15	)		€	23
Partner relationships		34,220			(24,055		)		10,165			34,220			(32,610		)		1,610
Technology		59,780			(56,030		)		3,750			59,780			(59,780		)		—
Non-compete agreement		10,800			(4,339		)		6,461			10,800			(5,881		)		4,919
Total		€	104,838		€	(84,429	)		€	20,409		€	104,838		€	(98,286	)		€	6,552

Amortization expense was €30.0 million for each of the years ended December 31, 2014 and December 31, 2015 and €13.9 million for the year ended December 31, 2016. The estimated future amortization expense related to intangible assets with definite lives as of December 31, 2016, assuming no subsequent impairment of the underlying assets, is as follows:



(in thousands)	Amortization
2017		€	3,163
2018		1,553
2019		1,546
2020		290
Total		€	6,552

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Debt - credit facility	12 Months Ended
Debt - credit facility	Dec. 31, 2016
Debt Disclosure [Abstract]
Debt - credit facility	Debt - credit facility We maintain a €50.0 million uncommitted credit facility at an interest rate of LIBOR + 1% per annum, which is guaranteed by Expedia, that may be terminated at any time by the lender. As of December 31, 2015 and December 31, 2016 we had €20.0 million and €0 million in borrowings outstanding on the consolidated balance sheet, respectively. The borrowings are classified as a short-term debt based on the lender’s ability to terminate the facility at any time.

Employee benefit plans	12 Months Ended
Employee benefit plans	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Employee benefit plans	Employee benefit plans For defined contribution plans, trivago pays contributions to publicly or privately administered pension insurance plans on a mandatory, contractual or voluntary basis. We have no further payment obligations once the contributions have been paid. The contributions are recognized as employee benefit expense when they are due. The amount of expense recognized for defined contribution pension plans was not material for the years ended December 31, 2014, 2015 and 2016.

Share-based awards and other equity instruments

12 Months Ended

Dec. 31, 2016

Share-based awards and other equity instruments

Option issuance prior to IPO

In connection with the controlling-interest acquisition of trivago by Expedia in 2013, certain outstanding trivago employee options as of the acquisition date were replaced with new trivago employee option awards exercisable into trivago Class A shares. The replacement awards were exchanged at acquisition date fair value and maintained their original service-based vesting schedule and strike price of €1. The original service-based vesting period for these awards are between one and three years. The options also contained conditions which allowed holders to put underlying shares to Expedia (and for which Expedia can call) during prescribed liquidity windows in 2016 and 2018, however holders are required to exercise options and hold underlying shares for a reasonable period of time prior to liquidation in order to participate in the risks and rewards of equity ownership. Of the 887 option awards outstanding as of January 1, 2014, 858 option awards were replaced at the time of Expedia’s acquisition of a controlling interest in us and the remaining were additional grants in 2013 which contained similar provisions as the replacement awards.

180, 77 and 146 Class A employee share options were granted in 2014, 2015 and 2016, respectively. Additionally, 62,178 and 74,580 Class B employee share options were granted in 2015 and 2016, respectively, which have economic and voting rights that are 1/1000 of a Class A option. Class A and Class B are presented as the same class of shares and Class B option awards are presented in terms of Class A equivalents. The majority of the employee share options granted in 2014, 2015, and 2016 had strike prices of €1. The remaining options in 2014 and 2015 were granted with strike prices which approximated the 2013 acquisition date fair value of trivago shares and the remaining 2016 options were granted with a strike price equal to the fair value of trivago shares estimated at the time of grant. All option awards granted in 2014, 2015, and 2016 contain service based vesting provisions between two and three years. The shares subscribed for underlying the grants in 2014, 2015, and 2016 are eligible to participate in prescribed liquidity events originally scheduled to occur in 2016, 2018 and 2020. Options granted with exercise prices in excess of €1 are not expected to participate in the risks and rewards of ownership for a reasonable period of time and are therefore accounted for as liability awards.

In the third quarter of 2015, 484 Class A equivalent trivago employee option awards were exercised for nominal proceeds. The underlying shares were held by employees in order to participate in the 2016 liquidity window. Upon exercise of these options, trivago paid employees’ personal tax liability related to the option exercise collateralized by the underlying shares and to be repaid by employees from 2016 liquidation proceeds. As the proceeds of €7.1 million were funded by Expedia, trivago recognized a related party payable for this amount. trivago’s extension of this nonrecourse loan to employees triggered an accounting modification and changed the classification of the awards from equity to liability accounting treatment, resulting in a one-time modification charge of €7.3 million and subsequent liability accounting treatment requiring remeasurement to fair value at each reporting period until settlement in 2016. The shareholder loan receivable was netted within the members’ liability balance which reflects the value of the liability awards, net of the loan.

There were certain shares held by trivago employees which were originally awarded in the form of share-based options pursuant to the trivago employee option plan and subsequently exercised by such employees. During the second quarter of 2016, Expedia exercised a call right on these shares and elected to do so at a premium to fair value, the aggregate payment of which, €62.5 million, was recorded as a Contribution from Parent in Members’ Equity. The exercise resulted in an incremental share-based compensation charge of approximately €43.7 million in the second quarter of 2016 pursuant to liability award treatment. The differential between the cash settlement amount and the incremental share-based compensation charge reflects share-based compensation expense recorded on these awards in previous periods. The €7.1 million related party payable and the €7.1 million shareholder loan receivable, netted within the members’ liability balance, was extinguished due to cash withheld from proceeds paid to employees by Expedia as part of this call right exercised by Expedia. The acquisition of these employee minority interests increased Expedia’s ordinary ownership of trivago to 63.5%.

In the third quarter of 2016, 38 class A equivalent trivago employee option awards were exercised for nominal proceeds. All of these awards were liability-classified awards and their subsequent subsequent settlement resulted in a reclassification of €4.2 million from Option liability to Reserves in equity. The options exercised were later called by Expedia, with the options exercised having strike prices in excess of €1. Expedia withheld all of the proceeds from exercise, which resulted in a €0.7 million payment to trivago and an offsetting impact to Reserves in equity.

Amendment to trivago option plan

In conjunction with the IPO of trivago N.V. there was a modification to the trivago option plan on December 22, 2016. The modification converted the options for shares in trivago GmbH into options for shares in trivago N.V. The adjustment to the terms of the options was equitable to the option holder, whereas the fair value calculated before and after the adjustment resulted in no incremental fair value. There was no change to the vesting or service conditions of the awards due to the amendment to the trivago option plan. The liquidity windows in 2018 and beyond are no longer in effect under the amended trivago option plan.

Furthermore, as part of the modification of options for shares in trivago GmbH to options for shares in trivago N.V., all awards are considered to be equity classified awards as of the modification date. Prior to the modification, certain awards with an exercise price higher than €1 were liability classified as the option holders were not expected to participate in the risks and rewards normally associated with equity share ownership for a reasonable period of time. However, with the modification, the employees no longer have the option for the Company to settle the options in cash and with the IPO the employees can now have access to a liquid market for the shares of trivago N.V., allowing them to participate in the risks and rewards or equity share ownership. The amendment to the plan and modification resulted in a €4.9 million reclassification of the liability for these options to Reserves in equity and the awards are classified as equity going forward.

2016 Omnibus Incentive Plan

In conjunction with the IPO, we established the trivago N.V. 2016 Omnibus Incentive Plan, which we refer to as the 2016 Plan. The maximum number of Class A shares available for issuance under the 2016 Plan is 34,711,009 Class A shares. Management board members, officers, employees and consultants of the company or any of our subsidiaries or affiliates, and any prospective directors, officers, employees and consultants of the company who have accepted offers of employment or consultancy from the company or our subsidiaries or affiliates (excluding supervisory board members) are eligible for awards under the 2016 Plan.

The 2016 Plan is administered by a committee of at least two members of our supervisory board, which we refer to as the plan committee. The plan committee must approve all awards to directors. Our management board may approve awards to eligible recipients other than directors, subject to annual aggregate and individual limits as may be agreed to with the supervisory board. Subject to applicable law or the listing standards of the applicable exchange, the plan committee may delegate to other appropriate persons the authority to grant equity awards under the 2016 Plan to our eligible award recipients.

Awards include options, share appreciation rights, restricted share units and other share-based and cash-based awards. Awards may be settled in stock or cash. The option exercise price for options under the 2016 Plan for Management board members shall not be less than the fair market value of a share as defined in the 2016 Plan on the relevant grant date. The option exercise price for options under the 2016 Plan for other eligible individuals can be less than the fair market value of a share as defined in the 2016 Plan on the relevant grant date. To the extent that listing standards of the applicable exchange require the company’s shareholders to approve any repricing of options, options may not be repriced without shareholder approval.

Options and share appreciation rights shall vest and become exercisable at such time and pursuant to such conditions as determined by the plan committee and as may be specified in an individual grant agreement. The plan committee may at any time accelerate the exercisability of any option or share appreciation right. Restricted shares may vest based on continued service, attainment of performance goals or both continued service and performance goals. The plan committee at any time may waive any of these vesting conditions.

Options and share appreciation rights will have a term of not more than ten years. The 2016 Plan will also have a ten year term, although awards outstanding on the date the 2016 Plan terminates will not be affected by the termination of the 2016 Plan.

As of December 31, 2016, there were no awards granted under the 2016 Plan.

trivago amended option plan

Under the trivago amended option plan, we may grant share options and other share-based awards to management board and supervisory board members, officers, employees and consultants. We issue new shares to satisfy the exercise or release of share-based awards.

The following table presents a summary of our share option activity in trivago N.V. equivalent shares:



	As of December 31, 2016
	Options	Weighted average exercise price			Remaining contractual life		Aggregate intrinsic value
						(In years)
Balance as of January 1, 2014	887		€	1
Granted	180		€	9,974
Balance as of December 31, 2014	1,067		€	1,683
Granted	139		€	3,871
Exercised	484		€	1
Balance as of December 31, 2015	722		€	3,239
Granted	221		€	80,926
Exercised	39		€	17,953
Cancelled	2		€	1
Balance as of December 31, 2016	902		€	21,637		0.77		€	68,235
Balance as of December 31, 2016 (trivago N.V. equivalents)	7,704,659
Exercisable as of December 31, 2016	517		€	209		0.77		€	89,663
Vested and expected to vest after December 31, 2016	902		€	21,637		0.77		€	68,235

As discussed above, the options legally exercised in 2015 were subject to an accounting modification that changed their classification from equity to liability awards. These awards remained subject to variable accounting treatment through their settlement date in June 2016. The total intrinsic value of share options exercised was €16.2 million and €3.0 million for the year ended December 31, 2015 and December 31, 2016, respectively.

As of December 31, 2014, 100 Class A option awards were subject to liability accounting. Of the outstanding options at December 31, 2015, 130 Class A and 7 Class B options (in terms of Class A equivalents options) were subject to liability accounting. Prior to the IPO, 93 Class A and 6 Class B options (in terms of Class A equivalents options) were subject to liability accounting. As of December, 31, 2016, no option awards are subject to liability accounting.

During the three years ended December 31, 2014, 2015 and 2016, we awarded share options as our only form of share-based compensation. The fair value of share options granted during the years ended December 31, 2014, 2015 and 2016 were estimated at the date of grant using the Black-Scholes option-pricing model, assuming the following weighted average assumptions:



	Year ended December 31,
	2014				2015			2016
Risk-free interest rate		1.31		%	1.31		%		1.31		%
Expected volatility		46		%	46		%		46		%
Expected life (in years)		2.98			1.82				2.68
Dividend yield		—		%	—		%		—		%
Weighted-average estimated fair value of options granted during the year		€	22,689		€	29,496			€	34,425

In 2014, 2015 and 2016, we recognized total share-based compensation expense of €2.4 million, €14.1 million and €53.7 million, respectively. There was no income tax benefit related to share-based compensation expense for 2014, 2015 and 2016. Additionally, €8 thousand, €103 thousand and €318 thousand of share-based compensation cost was capitalized in 2014, 2015 and 2016, respectively, as part of software development costs.

Cash received from share-based award exercises for the years ended December 31, 2014, 2015 and 2016 was €0, €10 thousand and €685 thousand, respectively.

As of December 31, 2016, there was approximately €9.3 million in unrecognized share-based compensation expense related to unvested share-based awards subject to equity treatment, which is expected to be recognized in expense in less than one year.

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

Redeemable noncontrolling interests

Income taxes

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Income taxes

The following table summarizes our income tax expense/(benefit):



	Year ended December 31,
(in thousands)	2014				2015				2016
Current income tax expense (benefit):
Germany		€	628			€	(1,032	)	€	11,405
Other countries		43				158			103
Current income tax expense (benefit)		671				(874		)	11,508
Deferred income tax (benefit) expense:
Germany		(9,315		)		(10,444		)	(4,838		)
Other countries		—				—			—
Deferred income tax (benefit) expense		(9,315		)		(10,444		)	(4,838		)
Income tax expense (benefit)		€	(8,644	)		€	(11,318	)	€	6,670

Reconciliation of German statutory income tax rate to effective income tax rate

The following table summarizes our income (loss) before income taxes allocated to Germany and to other countries:



	Year ended December 31,
(in thousands)	2014				2015				2016
Germany		€	(32,033	)		€	(50,446	)		€	(32,985	)
Other countries		293				(238		)		(11,736		)
Income (loss) before income taxes		€	(31,740	)		€	(50,684	)		€	(44,721	)

A reconciliation of amounts computed by applying the German statutory income tax rate to income from continuing operations before income taxes to total income tax expense (benefit) is as follows:



	Year ended December 31,
(in thousands)	2014				2015				2016
Income (loss) before income taxes		€	(31,740	)		€	(50,684	)		€	(44,721	)
Income tax expense at German tax rate (31.23%)		(9,912		)		(15,829		)		(13,964		)
Foreign rate differential		(11		)		34				219
Expected tax expense (benefit)		(9,923		)		(15,795		)		(13,745		)
Tax effect from:
Non-deductible share-based compensation		744				4,409				16,875
Non-deductible corporate costs		470				882				1,306
Changes in uncertain tax positions		—				(1,666		)		—
Movement in valuation allowance		—				98				1,921
Other differences		65				754				313
Income tax expense (benefit)		€	(8,644	)		€	(11,318	)		€	6,670

Our effective tax rate was 27.2% in 2014, 22.3% in 2015 and (14.9)% in 2016. This is due to non-deductible share-based compensation of (pre-tax) €2.4 million in 2014, €14.1 million in 2015 and €53.7 million in 2016. Furthermore, corporate costs were pushed down from Expedia (pre-tax) €1.5 million for 2014, €2.8 million for 2015 and €4.2 million for 2016, which are non-deductible for tax purposes. Additional details on the movement in valuation allowance and changes in uncertain tax positions are included below.

Other differences relate to one-off items during the year. In 2015, €520 thousand of the total €852 thousand was related to the non-tax deductible expense for the release of a contingent asset at the level of trivago GmbH. The remainder of the other differences amount in 2015 and 2016 relate to various small non-deductible expenses at the level of trivago GmbH.

Uncertain tax positions

A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows:



	Year Ended December 31,
(in thousands)	2014			2015				2016
Balance, beginning of year		€	1,545		€	1,666			€	—
Reductions due to lapsed statute of limitations during current year					(1,666		)		—
Interest and penalties		121			—				—
Balance, end of year		€	1,666		€	—			€	—

In 2013, an uncertain tax position was provided for related to the deductibility of certain compensation payments in 2010 and 2011. In 2015, a tax audit was finalized for the years 2009 through to 2012. This resulted in a full release of the uncertain tax position. There are no uncertain tax positions provided for in 2016.

Deferred income taxes

As of December 31, 2015 and 2016, the significant components of our deferred tax assets and deferred tax liabilities were as follows:



	Year Ended December 31,
(in thousands)	2015			2016
Deferred tax assets:
Prepaid expense and other current assets	€	683		€	1,285
Accounts payable, other	456			5
Net operating loss and tax credit carryforwards	110			3,566
Other	750			1,331
Total deferred tax assets	1,998			6,187
Less valuation allowance	(98		)	(3,550		)
Net deferred tax assets	1,900			2,637
Deferred tax liabilities:
Intangible assets, net	59,301			54,972
Property and equipment	594			812
Other	—			9
Total deferred tax liabilities	59,894			55,793
Net deferred tax asset/(liability)	€	(57,994	)	€	(53,156	)

As of December 31, 2016, we had net operating loss carryforwards (“NOLs”) for a tax-effected amount of approximately €3.6 million. The tax-effected NOL carryforwards increased from the amount recorded as of December 31, 2015 primarily due to pre-tax losses at the level of the trivago N.V. (€3.2 million) and myhotelshop Germany (€0.4 million). trivago N.V. is a Dutch company, however has its tax residency in Germany. If not utilized, the tax-effected NOL carryforwards of €3.6 million may be carried forward indefinitely.

As of December 31, 2016, we had a valuation allowance for a tax-effected amount of approximately €3.6 million related to the NOL carryforwards for which it is more likely than not the tax benefit will not be realized. The tax-effected valuation allowance increased by €3.5 million from the amount recorded as of December 31, 2015. Of the €3.5 million increase in tax-effected valuation allowance, €1.6 million is related to tax losses which have arisen as part of the IPO in 2016 and which were included directly in equity. If recognized, the total amount of €3.6 million unrecognized tax benefits would impact the effective tax rate, that is the unrecognized tax benefits would affect (if recognized) the tax provision within continuing operations.

The amount of the deferred tax asset considered realizable, however, could be adjusted if estimates of future taxable income during the carryforward period change, or if objective negative evidence in the form of cumulative losses is no longer present and additional weight may be given to subjective evidence such as our projections for growth.

The total cumulative amount of undistributed earnings related to investments in certain foreign subsidiaries where the foreign subsidiary has or will invest undistributed earnings indefinitely was insignificant (below €0.1 million) as of December 31, 2016 and therefore we have not provided for deferred income taxes on this taxable temporary difference. In the event we distribute such earnings in the form of dividends or otherwise, these would be tax exempt for all investments located in Europe. Any capital gains on the sale of participations would be 95% exempt under German tax law.

The Company is subject to audit by federal, state, local and foreign income tax authorities. The German tax authorities have finalized their tax audit of trivago’s German federal income tax returns for the periods ended December 31, 2009 through December 31 2012 and no material corrections were identified. Currently, there are no tax returns for trivago or subsidiaries under audit. As of December 31, 2016, for trivago and its subsidiaries, statute of limitations for tax years 2013 through 2016 remain open to examination by German tax authorities.

Redeemable noncontrolling interests

12 Months Ended

Dec. 31, 2016

Noncontrolling Interest [Abstract]

Noncontrolling interest exists in entities majority owned by us, which are carried at fair value as the noncontrolling interests contain certain rights, whereby we may acquire and the minority shareholders may sell to us the additional shares of the companies. A reconciliation of redeemable noncontrolling interest for the years ended December 31, 2015 and December 31, 2016 is as follows:



	Year ended December 31,
(in thousands)	2015				2016
Balance, beginning of the period		€	0			€	2,076
Acquisition of redeemable noncontrolling interests		2,230				0
Net loss attributable to noncontrolling interests		(239		)		(995		)
Fair value adjustments through members’ equity		239				995
Currency translation adjustments and other		(154		)		129
Change in ownership of noncontrolling interest		—				€	(1,854	)
Balance, end of period		€	2,076			€	351

For information on redeemable noncontrolling interest acquired during 2015, see Note 3 - Acquisitions.

As of December 31, 2015, the fair value of the redeemable noncontrolling interest has been adjusted by €239 thousand for the net loss attributable to noncontrolling interest. A fair value adjustment has been recorded of €239 thousand to reflect the fair value of the noncontrolling interest for the year ended December 31, 2015.

As of December 31, 2016, the fair value of the redeemable noncontrolling interest has been adjusted by €995 thousand for the net loss attributable to the noncontrolling interest in myhotelshop and the noncontrolling interest in base7 through the date of acquisition. A total fair value adjustment has been recorded of €995 thousand to reflect the fair value of the noncontrolling interests for the year ended December 31, 2016. On December 22, 2016, we acquired the remaining noncontrolling interest in base7. As the change in ownership interest does not result in a loss of control, the acquisition is considered an equity transaction. Consequently, we have eliminated the redeemable noncontrolling interest of base7 and changes in redeemable noncontrolling interest due to attributed earnings and foreign exchange gains/losses as of December 22, 2016.

Stockholders'/members' equity	12 Months Ended
Stockholders'/members' equity	Dec. 31, 2016
Equity [Abstract]
Stockholders'/members' equity	Stockholders'/members' equity Subscribed capital (prior to the corporate reorganization, see Note 1) The historical financial statements of trivago GmbH and its controlled subsidiaries made reference to the members’ equity as trivago GmbH Class A units and trivago GmbH Class B units. The equity of a GmbH was not unitized into shares under German corporate law. However, pursuant to the company’s articles of association, we unitized members’ equity into trivago GmbH Class A units and Class B units, with each trivago GmbH Class B unit having 1/1,000 of the voting rights of a trivago GmbH Class A unit. Class A and Class B common stock (after the corporate reorganization, see Note 1) As of December 31, 2016, we had ADSs representing 30,026,635 Class A shares outstanding, 209,008,088 Class B shares outstanding and the Founders will have the right to exchange their shares in trivago GmbH for 110,791,880 Class A shares or Class B shares in trivago N.V. subject to applicable limitations imposed under federal securities law. Class A and Class B common stock has a par value of €0.06 and €0.60, respectively. The holder of our Class B shares, Expedia, is entitled to ten votes per share, and holders of our Class A shares are entitled to one vote per share. All other terms and preferences of Class A and Class B common stock are the same. Reserves Reserves primarily represents the effects of pushdown accounting applied due to the change in control in 2013 in addition to share premium as result of the corporate reorganization and IPO. See Note 1 - Organization and basis of presentation. Accumulated other comprehensive income (loss) Accumulated other comprehensive income represents foreign currency translation adjustments for our subsidiaries in foreign locations. As of December 31, 2016, we do not expect to reclassify any amounts included in accumulated other comprehensive income (loss) into earnings during the next 12 months. Contribution from Parent The beginning contribution from Parent balance represents the pushdown of share-based compensation expense from Expedia. The change year over year primarily relates to additional share-based compensation expense as well as Expedia corporate expenses allocated to trivago. See Note 1 - Organization and basis of presentation, Note 9 - Share-based awards and other equity instruments and Note 16 - Related party transactions. Dividends In December 2016, trivago GmbH agreed to effect a one-time dividend payment in respect of fiscal year 2016. The dividend is in the amount of €0.5 million and will be paid to shareholders of record prior to the IPO, resulting in a €0.2 million cash outflow to trivago N.V.

Commitments and Contingencies Disclosure [Abstract]

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 4.E)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Section 50
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644

Reference 5: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e))
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(31))
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 4.C)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(30))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(d))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

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-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

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+ Details

Earnings per share

12 Months Ended

Dec. 31, 2016

Earnings Per Share [Abstract]

Earnings per share

Basic and diluted earnings per share of Class A and Class B common stock is computed by dividing net income attributable to trivago N.V., after adjusting for noncontrolling interest as a result of the corporate reorganization and IPO, for the period from December 16, 2016 (effective date of the corporate reorganization and IPO) through December 31, 2016, by the weighted average number of Class A and Class B common stock outstanding during the same period. There were no shares of Class A or Class B common stock outstanding prior to December 16, 2016, therefore no earnings per share information has been presented for any period prior to that date.

The following table presents our basic and diluted earnings per share:



(In thousands, except per share data)	December 16, 2016 through December 31, 2016
Numerator:
Net income		€	1,185
Less: net income attributable to noncontrolling interest		285
Net income attributable to trivago N.V.		€	900
Denominator:
Weighted average shares of Class A and Class B common stock outstanding - basic and diluted		237,811

Earnings per share attributable to trivago N.V. available to Class A and Class B common stockholders - basic and diluted		€	0.00

Commitments and contingencies

12 Months Ended

Dec. 31, 2016

Commitments and contingencies

Credit facility, purchase obligations and guarantees

We have commitments and obligations which include purchase commitments, which could potentially require our payment in the event of demands by third parties or contingent events. Commitments and obligations as of December 31, 2016 were as follows:



	By Period
(in thousands)	Total			Less than 1 year			1 to 3 years			3 to 5 years			More than 5 years
Purchase obligations		€	40,374		€	31,374		€	9,000		€	—		€	—

Our purchase obligations represent minimum obligations we have under agreements with certain of our vendors and marketing partners. These minimum obligations are less than our projected use for those periods. Payments may be more than the minimum obligations based on actual use.

In addition, our redeemable noncontrolling interest in myhotelshop contains certain put/call rights whereby we may acquire and the minority shareholders may sell to us the minority shares of the Company. See Note 3 - Acquisitions for further information.

Lease commitments

We have contractual obligations in the form of operating leases for office space and related office equipment. Certain leases contain periodic rent escalation adjustments and renewal options. Rent expense related to such leases is recorded on a straight-line basis over the lease term. Lease obligations expire at various dates through 2038. For the years ended December 31, 2014, 2015 and 2016, our rental expense was €2.2 million, €3.3 million and €4.6 million, respectively.

We have operating lease agreements that require us to decommission physical space for which we have not yet recorded an asset retirement obligation. Due to the uncertainty of specific decommissioning obligations, timing and related costs, we cannot reasonably estimate an asset retirement obligation for these properties and we have not recorded a liability at this time for such properties.

The following table presents our estimated future minimum rental payments under operating leases with noncancelable lease terms that expire after December 31, 2016:



(in thousands)	Year ending December 31,
2017		€	4,035
2018		6,367
2019		8,324
2020		6,799
2021		6,799
2022 and thereafter		38,433
Total		€	70,757

Legal proceedings

In the ordinary course of business, we are a party to various lawsuits. Management does not expect these lawsuits to have a material impact on the liquidity, results of operations, or financial condition of trivago. We also evaluate other potential contingent matters, including value-added tax, excise tax, sales tax, transient occupancy or accommodation tax and similar matters. As of December 31, 2015 and 2016, there were no material contingent matters or lawsuits.

Related party transactions	12 Months Ended
Related party transactions	Dec. 31, 2016
Related Party Transactions [Abstract]
Related party transactions	Related party transactions Relationship with Expedia, Inc. We have commercial relationships with Expedia and many of its affiliated brands, including Brand Expedia, Hotels.com, Orbitz, Travelocity, Wotif and ebookers. These are oral arrangements or arrangements terminable at will or upon three to seven days’ prior notice by either party and on customary commercial terms that enable Expedia’s brands to advertise on our platform, and we receive payment for users we refer to them. We are also party to a letter agreement pursuant to which Expedia refers traffic to us when a particular hotel or region is unavailable on the applicable Expedia website. Related-party revenue from Expedia of €100.2 million, €194.2 million and €268.2 million for the years ended December 31, 2014, 2015 and 2016, respectively, primarily consists of click through fees and other advertising services provided to Expedia and its subsidiaries. These amounts are recorded at contract value, which we believe is a reasonable reflection of the value of the services provided. Related-party revenue represented 32%, 39% and 36%of our total revenue for the years ended December 31, 2014, 2015 and 2016, respectively. Our operating expenses include a related-party shared services fee, of €1.5 million, €2.8 million and €4.2 million for the years ended December 31, 2014, 2015 and 2016, respectively. This shared service fee is comprised of allocations from Expedia for legal, tax, treasury, audit and corporate development costs and includes an allocation of employee compensation within these functions. These expenses were allocated based on a number of factors including headcount, estimated time spent and operating expenses which trivago considers reasonable estimates. These amounts may have been different had trivago operated as an unaffiliated entity. The related party trade receivable balances with Expedia and its subsidiaries reflected in our consolidated balance sheets as of December 31, 2015 and 2016 were €23.6 million and €16.5 million, respectively. The related party trade payable balance with Expedia and its subsidiaries reflected in our consolidated balance sheets as of December 31, 2015 was €7.1 million and immaterial as of December 31, 2016. Guarantee On September 5, 2014, we entered into an uncommitted credit facility with Bank of America Merrill Lynch International Ltd., one of the underwriters of our initial public offering, with a maximum principal amount of €10.0 million. Advances under this facility bear interest at a rate of LIBOR plus 1.0% per annum. This facility may be terminated at any time by the lender. Our obligations under this facility are guaranteed by Expedia. On December 19, 2014, we entered into an amendment to this facility pursuant to which the maximum principal amount was increased to €50.0 million. We utilized €20.0 million of our €50.0 million credit facility to fund capital requirements in 2015. During the year ended December 31, 2016, we utilized an additional €20.0 million under our credit facility and subsequently repaid a total of €40.0 million of this obligation. On July 23, 2015, we entered into an agreement to design and build our new headquarters building in Düsseldorf, Germany. As part of that agreement, Expedia has guaranteed certain payments due by trivago under the contract which are expected to commence on May 31, 2017. The guarantee by Expedia ends upon receipt of a bank guarantee by trivago, but in any case not later than December 31, 2018. Loan from Expedia In 2014, Expedia issued a loan of €1.0 million to trivago in conjunction with trivago’s acquisition of Rheinfabrik in 2014. The loan was subsequently repaid by trivago during 2015. See Note 3 - Acquisitions. Services agreement On May 1, 2013, we entered into an Assets Purchase Agreement, pursuant to which Expedia purchased certain computer hardware and software from us, and a Data Hosting Services Agreement, pursuant to which Expedia provides us with certain data hosting services relating to all of the servers we use that are located within the United States. Either party may terminate the Data Hosting Services Agreement upon 30 days’ prior written notice. For each of the years ended December 31, 2014, 2015 and 2016, we paid Expedia €21 thousand annually for these data hosting services. Services and support agreement On September 1, 2016, we entered into a Services and Support Agreement, pursuant to which Expedia agreed to provide us with certain services in connection with localizing content on our websites, such as translation services. Either party may terminate the Services and Support Agreement upon 90 days’ prior notice. We have not incurred material expenses under this agreement.

Segment information

12 Months Ended

Dec. 31, 2016

Segment Reporting [Abstract]

Segment information

Beginning in the second quarter of 2016, management identified three reportable segments, which correspond to our three operating segments: the Americas, Developed Europe and Rest of World. We have restated our segments for the years ended December 31, 2014 and December 31, 2015. The change from one to three reportable segments was the result of a shift in the Company’s focus on managing the business to reflect unique market opportunities and competitive dynamics inherent in our business within each of our operating segments. Our Americas segment is growing and becoming a larger share of consolidated referral revenue and has the second largest exposure to our extensive marketing and advertising campaigns. Our Americas segment is currently comprised of Argentina, Brazil, Canada, Chile, Colombia, Ecuador, Mexico, Peru, the United States and Uruguay. Our Developed Europe segment represents the region where we are a well matured brand and is comprised of Austria, Belgium, Denmark, Finland, France, Germany, Ireland, Italy, the Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. The Developed Europe region was our initial region of operations and has the largest exposure to our extensive marketing and advertising campaigns. Our Rest of World segment represents all regions outside of the Americas and Developed Europe and is in its early stages of growth. The top countries by revenue in the Rest of World segment include Australia, Hong Kong, Japan, New Zealand and Poland.

We determined our operating segments based on how our chief operating decision makers manage our business, make operating decisions and evaluate operating performance. Our primary operating metric is Return on Advertising Spend, or ROAS, for each of our segments, which compares referral revenue to advertising spend. ROAS includes the allocation of revenue by segment which is based on the location of the website, or domain name, regardless of where the consumer resides. This is consistent with how management monitors and runs the business.

Corporate and Eliminations also includes all corporate functions and expenses except for direct advertising. In addition, we record amortization of intangible assets and any related impairment, as well as share-based compensation expense, restructuring and related reorganization charges, legal reserves, occupancy tax and other, and other items excluded from segment operating performance in Corporate and Eliminations. Such amounts are detailed in our segment reconciliation below.

The following tables present our segment information for the years ended December 31, 2014, 2015 and 2016. As a significant portion of our property and equipment is not allocated to our operating segments and depreciation is not included in our segment measure, we do not report the assets by segment as it would not be meaningful. We do not regularly provide such information to our chief operating decision makers.



	Year Ended December 31, 2014
(in thousands)	Developed Europe			Americas				Rest of World				Corporate & Eliminations			Total
Referral revenue		€	210,241		€	73,316			€	25,595			€	0		€	309,152
Other revenue		0			0				0				180			180
Total revenue		210,241			73,316				25,595				180			309,332
Advertising spend		162,358			81,110				27,899				0			271,367
ROAS contribution		€	47,883		€	(7,794	)		€	(2,304	)		€	180		€	37,965
Costs and expenses:
Cost of revenue, including related party, excluding amortization																1,443
Other selling and marketing⁽¹⁾																14,867
Technology and content																15,388
General and administrative, including related party shared service fee																6,536
Amortization of intangible assets																30,025
Operating income (loss)																(30,294		)
Other income (expense)
Interest expense																(11		)
Other, net																(1,435		)
Total other income (expense), net																(1,446		)
Income (loss) before income taxes																(31,740		)
Provision for income taxes																(8,644		)
Net loss																€	(23,096	)

(1) Represents all other sales and marketing, excluding advertising spend, as advertising spend is tracked by reporting segment.



	Year Ended December 31, 2015
(in thousands)	Developed Europe			Americas			Rest of World				Corporate & Eliminations			Total
Referral revenue		€	259,568		€	171,910		€	58,762			€	0		€	490,240
Other revenue		0			0			0				2,843			2,843
Total revenue		259,568			171,910			58,762				2,843			493,083
Advertising spend		194,886			169,415			67,872				0			432,173
ROAS contribution		€	64,682		€	2,495		€	(9,110	)		€	2,843		€	60,910
Costs and expenses:
Cost of revenue, including related party, excluding amortization															2,946
Other selling and marketing⁽¹⁾															29,046
Technology and content															28,693
General and administrative, including related party shared service fee															18,065
Amortization of intangible assets															30,030
Operating income (loss)															(47,870		)
Other income (expense)
Interest expense															(147		)
Other, net															(2,667		)
Total other income (expense), net															(2,814		)
Income (loss) before income taxes															(50,684		)
Provision for income taxes															(11,318		)
Net loss															€	(39,366	)

(1) Represents all other sales and marketing, excluding advertising spend, as advertising spend is tracked by reporting segment.



	Year Ended December 31, 2016
(in thousands)	Developed Europe			Americas			Rest of World				Corporate & Eliminations			Total
Referral revenue		€	348,909		€	286,398		€	110,517			€	0		€	745,824
Other revenue		0			0			0				8,345			8,345
Total revenue		348,909			286,398			110,517				8,345			754,169
Advertising spend		257,471			243,176			122,805				0			623,452
ROAS contribution		€	91,438		€	43,222		€	(12,288	)		€	8,345		€	130,717
Costs and expenses:
Cost of revenue, including related party, excluding amortization															4,273
Other selling and marketing(1)															51,277
Technology and content															51,658
General and administrative, including related party shared service fee															54,097
Amortization of intangible assets															13,857
Operating income (loss)															(44,445		)
Other income (expense)
Interest expense															(137		)
Other, net															(139		)
Total other income (expense), net															(276		)
Income (loss) before income taxes															(44,721		)
Provision for income taxes															6,670
Net loss															€	(51,391	)

(1) Represents all other sales and marketing, excluding advertising spend, as advertising spend is tracked by reporting segment.

Geographic information

The following table presents revenue by geographic area for the years ended December 31, 2014, 2015 and 2016. Referral revenue was allocated by country using the same methodology as the allocation of segment revenue, while non-referral revenue was allocated based upon the location of the customer using the service.



	Year ended December 31,
(in thousands)	2014			2015			2016
Total Revenues
United States		€	54,560		€	128,891		€	199,423
Germany		57,826			67,470			76,599
United Kingdom		46,707			61,541			86,745
Spain		25,776			29,206			37,715
Italy		23,197			26,394			31,272
Canada		15,422			23,156			33,112
All other countries		85,844			156,425			289,303
		€	309,332		€	493,083		€	754,169

The following table presents property and equipment, net for Germany and all other countries, as of December 31, 2015 and 2016:



(in thousands)		Years ended December 31,
	2015			2016
Property and equipment, net
Germany		€	12,676		€	46,098
All other countries		177			764
		€	12,853		€	46,862

Schedule of purchase price allocation

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

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+ Details

Significant accounting policies (Policies)	12 Months Ended
Significant accounting policies (Policies)	Dec. 31, 2016
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The corporate reorganization, as described above, is considered a transaction between entities under common control. As a result, the financial statements for periods prior to the IPO and the corporate reorganization are the financial statements of trivago GmbH as the predecessor to the Company for accounting and reporting purposes. Unless otherwise specified, “the Company” refers to trivago N.V., and trivago GmbH and its respective subsidiaries throughout the remainder of these notes. These consolidated financial statements reflect Expedia’s basis of accounting due to the change in control in 2013 when Expedia acquired a controlling ownership in trivago, as we elected the option to apply pushdown accounting in the period in which the change in control event occurred. Expedia incurs certain costs on behalf of trivago. The consolidated financial statements reflect the allocation of certain of Expedia’s corporate expenses to trivago (see Note 16 - Related Parties for further information). We recorded all corporate allocation charges from Expedia within our consolidated statement of operations and as a contribution from Parent within the consolidated statement of changes in equity. Our management believes that the assumptions underlying the consolidated financial statements are reasonable. However, this financial information does not necessarily reflect the future financial position, results of operations and cash flows of trivago, nor does it reflect what the historical financial position, results of operations and cash flows of trivago would have been had we been a stand-alone company during the periods presented.
Consolidation	Consolidation Our consolidated financial statements include the accounts of trivago and entities we control. All significant intercompany balances and transactions have been eliminated in consolidation. We record noncontrolling interest in our consolidated financial statements to recognize the minority ownership interest in our consolidated subsidiaries. Noncontrolling interest in the earnings and losses of consolidated subsidiaries represent the share of net income or loss allocated to members or partners in our consolidated entities, which includes the noncontrolling interest share of net income or loss from our redeemable noncontrolling interest entities and our noncontrolling interest in trivago GmbH. As discussed in Note 1, as a result of the corporate reorganization, trivago N.V. consolidates trivago GmbH and trivago GmbH is considered to be the predecessor to trivago N.V. for accounting and reporting purposes. We characterize the 31.7% minority interest in trivago GmbH as of December 31, 2016 as a noncontrolling interest and classify it as a component of stockholders’ equity in our consolidated financial statements. Noncontrolling interests with shares redeemable at the option of the minority holders in myhotelshop and base7 have been included in redeemable noncontrolling interests. We classify the redeemable noncontrolling interest as a mezzanine equity below non-current liabilities in our consolidated financial statements. See Note 11 - Redeemable noncontrolling interests for further discussion.
Accounting estimates	Accounting estimates We use estimates and assumptions in the preparation of our consolidated financial statements in accordance with accounting principles generally accepted in the United States (“GAAP”). Our estimates and assumptions affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of our consolidated financial statements. These estimates and assumptions also affect the reported amount of net income or loss during any period. Our actual financial results could differ significantly from these estimates. The significant estimates underlying our consolidated financial statements include revenue recognition, intangible assets and goodwill, redeemable noncontrolling interest, acquisition purchase price allocations, and share-based compensation.
Revenue recognition	Seasonality We experience seasonal fluctuations in the demand for our services as a result of seasonal patterns in travel. For example, our revenue is generally highest in the second and third quarters of each year. Our revenue typically decreases in the fourth quarter. We generally expect to experience higher profits in the second half of the year as we typically have higher marketing expenses in the first half of the year in advance of high travel seasons. Seasonal fluctuations affecting our revenue also affect the timing of our cash flows. We typically receive payment for referrals within 30 days of the referral. Therefore, our cash flow varies seasonally with a slight lag to our revenue, and is significantly affected by the timing of our advertising spending. The continued growth of our offerings in countries and areas where seasonal travel patterns vary may influence the typical trend of our seasonal patterns in the future. Revenue recognition We recognize revenue from services rendered when the following four revenue recognition criteria are met: persuasive evidence of an arrangement exists, services have been rendered, the price is fixed or determinable, and collectability is reasonably assured. Revenue is generated each time a visitor to one of our websites or apps clicks on a hotel room offer in our search results and is referred to one of our advertisers. Advertisers pay on a per referral basis, with the aforementioned visitor click-through being considered a single referral. Given the nature of the industry, it is not unusual for referrals to be generated from automated scripts designed to browse and collect data on our websites. However, review processes are in place to identify anomalies to ensure revenue recognition is appropriate. Pricing is determined through a competitive bidding process whereby advertisers bid on their placement priority for a specific room offer within each room listing. Bids can be placed as often as daily, and changes in bids are applied on a prospective basis on the following day. Additionally, a portion of our revenue is generated through subscription-based services earned through trivago Hotel Manager Pro applications. This revenue is recognized ratably over the subscription period with deferred revenue recognized upon receipt of payment in advance of revenue recognition.
Cost of revenue	Cost of revenue Cost of revenue consists of expenses that are directly or closely correlated to revenue generation, including data center costs, salaries and share-based compensation for our data center operations staff and our customer service team who are directly involved in revenue generation.
Restricted cash	Restricted cash Restricted cash primarily consists of funds held as guarantees in connection with corporate leases and funds held in escrow accounts in the event of default on corporate credit card statements. The carrying value of restricted cash approximates its fair value.
Accounts receivable	Accounts receivable Accounts receivable are generally due within thirty days and are recorded net of an allowance for doubtful accounts. We determine our allowance by considering a number of factors, including the length of time trade accounts receivable are past due, previous loss history, a specific customer’s ability to pay its obligations to us, and the condition of the general economy and industry as a whole.
Property and equipment, net including software and website capitalization	Property and equipment, net including software and website capitalization We record property and equipment at cost, net of accumulated depreciation and amortization. We compute depreciation using the straight-line method over the estimated useful lives of the assets, which is generally three to five years for computer equipment, capitalized software development and furniture and other equipment. We amortize leasehold improvement using the straight-line method, over the shorter of the estimated useful life of the improvement or the remaining term of the lease, the majority of which will be fully amortized through 2018. Certain direct development costs associated with website and internal-use software are capitalized during the application development stage. Capitalized costs include external direct costs of services and payroll costs (including share-based compensation). The payroll costs are for employees devoting time to the software development projects principally related to website and mobile app development, including support systems, software coding, designing system interfaces and installation and testing of the software. These costs are recorded as property and equipment and are generally amortized over a period of three years beginning when the asset is ready for use. Costs incurred for enhancements that are expected to result in additional features or functionality are capitalized and amortized over the estimated useful life of the enhancements, which is generally a period of three years. Costs incurred during the preliminary project stage, as well as maintenance and training costs, are expensed as incurred.
Leases	Leases We lease office space in several countries under non-cancelable lease agreements. We generally lease our office facilities under operating lease agreements. We recognize rent expense on a straight-line basis over the lease period. Any lease incentives are recognized as reductions of rental expense on a straight-line basis over the term of the lease. The lease term begins on the date we become legally obligated for the rent payments or when we take possession of the office space, whichever is earlier. We establish assets and liabilities for the estimated construction costs incurred under lease arrangements where we are considered the owner for accounting purposes only, or build-to-suit leases, to the extent that we are involved in the construction of structural improvements or take construction risk prior to commencement of a lease. In July 2015, we entered into a lease for new corporate headquarters with 26,107 square meters of office space. Pursuant to the lease, the Landlord will build this office building in Düsseldorf, Germany. As a result of our involvement in the construction project and our responsibility for paying a portion of the costs of normal finish work and structural elements of the premises, the Company was deemed for accounting purposes to be the owner of the premises during the construction period pursuant to build-to-suit lease accounting guidance under ASC 840. Therefore, the Company recorded project construction costs during the construction period incurred by the landlord as a construction-in-progress asset and a related construction financing obligation on our consolidated balance sheets. The amounts that the Company has paid or incurred for normal tenant improvements and structural improvements had also been recorded as part of the construction-in-progress asset. We have a lease that includes both building and land. We have bifurcated our lease payments pursuant to the premises into: a portion that is allocated to the building (a reduction to the financing obligation); and a portion that is allocated to the land on which the building was constructed. The portion of the lease obligations allocated to the land is treated as an operating lease that commenced in July 2015.
Business combinations	Business combinations We assign the value of the consideration transferred to acquire a business to the tangible assets and identifiable intangible assets acquired and liabilities assumed on the basis of their fair values at the date of acquisition. Any excess purchase price over the fair value of the net tangible and intangible assets acquired is allocated to goodwill. When determining the fair values of assets acquired and liabilities assumed, management makes significant estimates and assumptions, especially with respect to intangible assets. Critical estimates in valuing certain intangible assets include but are not limited to future expected cash flows from customer relationships and discount rates. Management’s estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates.
Recoverability of goodwill and indefinite-lived intangible assets	Recoverability of goodwill and indefinite-lived intangible assets Goodwill is assigned to our three reporting units, which correspond to our three operating segments, on the basis of their relative fair values as of the date of change in reporting units. We assess goodwill and indefinite-lived assets, neither of which are amortized, for impairment annually in the fourth quarter of the year, or more frequently, if events and circumstances indicate that an impairment may have occurred. In the evaluation of goodwill for impairment, we typically first perform a qualitative assessment to determine whether it is more likely than not that the fair value of each reporting unit is less than its carrying amount. If so, we perform a quantitative assessment and compare the fair value of that reporting unit to its carrying value. If the carrying value of a reporting unit exceeds its fair value, the goodwill of that reporting unit is potentially impaired and we proceed to step two of the impairment analysis. In step two of the analysis, we will record an impairment loss equal to the excess of the carrying value of the reporting unit’s goodwill over its implied fair value should such a circumstance arise. Periodically, we may choose to forgo the initial qualitative assessment and perform quantitative analysis to assist in our annual evaluation. We generally base the measurement of fair value of our three reporting units on a blended analysis of the present value of future discounted cash flows and market valuation approach. The discounted cash flows model indicates the fair value of the reporting unit based on the present value of the cash flows that we expect the reporting unit to generate in the future. Our significant estimates in the discounted cash flows model include our weighted average cost of capital, long-term rate of growth and profitability of our business. The market valuation approach indicates the fair value of the business based on a comparison of the reporting unit to comparable publicly traded firms in similar lines of business. Our significant estimates in the market approach model include identifying similar companies with comparable business factors, such as size, growth, profitability, risk and return on investment and assessing comparable revenue and operating income multiples in estimating the fair value of the reporting unit. We believe the weighted use of discounted cash flows and market approach is the best method for determining the fair value of our reporting units because these are the most common valuation methodologies used within the travel and Internet industries; and the blended use of both models compensates for the inherent risks associated with either model if used on a stand-alone basis. In addition to measuring the fair value of our reporting units as described above, we consider the combined carrying and fair values of our reporting units in relation to the company’s total fair value. In our evaluation of our indefinite-lived intangible assets, we typically first perform a qualitative assessment to determine whether the fair value of the indefinite-lived intangible assets is more likely than not impaired. If so, we perform a quantitative assessment and an impairment charge is recorded for the excess of the carrying value of the indefinite-lived intangible assets over the fair value. We base our measurement of the fair value of our indefinite-lived intangible assets, which consist of trade name, trademarks, and domain names using the relief-from-royalty method. This method assumes that the trade name and trademarks have value to the extent that their owner is relieved of the obligation to pay royalties for the benefits received from them. As with goodwill, periodically, we may choose to forgo the initial qualitative assessment and perform a quantitative analysis in our annual evaluation of indefinite-lived intangible assets.
Recoverability of intangible assets with definite lives and other long-lived assets	Recoverability of intangible assets with definite lives and other long-lived assets Intangible assets with definite lives and other long-lived assets are carried at cost and are amortized on a straight-line basis over their estimated useful lives of generally less than seven years. We review the carrying value of long-lived assets or asset groups, including property and equipment whenever events or changes in circumstances indicate that the carrying amount of the assets might not be recoverable. Factors that would necessitate an impairment assessment include a significant adverse change in the extent or manner in which an asset is used, a significant adverse change in legal factors or the business climate that could affect the value of the asset, or a significant decline in the observable market value of an asset, among others. If such facts indicate a potential impairment, we would assess the recoverability of an asset group by determining if the carrying value of the asset group exceeds the sum of the projected undiscounted cash flows expected to result from the use and eventual disposition of the assets over the remaining economic life of the primary asset in the asset group. If the recoverability test indicates that the carrying value of the asset group is not recoverable, we will estimate the fair value of the asset group using appropriate valuation methodologies, which would typically include an estimate of discounted cash flows. Any impairment would be measured as the difference between the asset group’s carrying amount and its estimated fair value.
Income taxes	Income taxes We record income taxes under the liability method. Deferred tax assets and liabilities reflect our estimation of the future tax consequences of temporary differences between the carrying amounts of assets and liabilities for book and tax purposes. We determine deferred income taxes based on the differences in accounting methods and timing between financial statement and income tax reporting. Accordingly, we determine the deferred tax asset or liability for each temporary difference based on the enacted tax rates expected to be in effect when we realize the underlying items of income and expense. We consider many factors when assessing the likelihood of future realization of our deferred tax assets, including our recent earnings experience by jurisdiction, expectations of future taxable income, and the carryforward periods available to us for tax reporting purposes, as well as other relevant factors. We may establish a valuation allowance to reduce deferred tax assets to the amount we believe is more likely than not to be realized. Due to inherent complexities arising from the nature of our businesses, future changes in income tax law, tax sharing agreements or variances between our actual and anticipated results of operations, we make certain judgments and estimates. Therefore, actual income taxes could materially vary from these estimates. We account for uncertain tax positions based on a two-step process of evaluating recognition and measurement criteria. The first step assesses whether the tax position is more likely than not to be sustained upon examination by the tax authority, including resolution of any appeals or litigation, based on the technical merits of the position. If the tax position meets the more likely than not criteria, the portion of the tax benefit greater than 50% likely to be realized upon settlement with the tax authority is recognized in the financial statements. Interest and penalties related to uncertain tax positions are classified in the financial statements as a component of income tax expense. Presentation of taxes in the statements of operations We present taxes that we collect from advertisers and remit to government authorities on a net basis in our consolidated statements of operations.
Foreign currency translation and transaction gains and losses	Foreign currency translation and transaction gains and losses The consolidated Financial Statements have been prepared in euros, the reporting currency. Certain of our operations outside of the Eurozone use the local currency as their functional currency. We translate revenue and expense at average exchange rates during the period and assets and liabilities at the exchange rates as of the consolidated balance sheet dates and include such foreign currency translation gains and losses as a component of other comprehensive income. Due to the nature of our operations and our corporate structure, we also have subsidiaries that have significant transactions in foreign currencies other than their functional currency. We record transaction gains and losses in our consolidated statements of operations related to the recurring remeasurement and settlement of such transactions.
Advertising expense	Advertising expense We incur advertising expense consisting of offline costs, including television and radio advertising, as well as online advertising expense to promote our brands. A significant portion of traffic from users is directed to our websites through our participation in display advertising campaigns on search engines, advertising networks, affiliate websites and social networking sites. We consider traffic acquisition costs to be indirect advertising fees. We expense the production costs associated with advertisements in the period in which the advertisement first takes place. We expense the costs of communicating the advertisement (e.g., television airtime) as incurred each time the advertisement is shown. These costs are included in selling and marketing expense in our consolidated statements of operations.
Share-based compensation	Share-based compensation All share-based compensation included in our consolidated financial statements relates to certain outstanding trivago employee options replaced with new trivago employee option awards exercisable into trivago Class A shares, in connection with the controlling-interest acquisition of trivago by Expedia in 2013. There were no options granted subsequent to the IPO through the end of the year. The following methods were used to measure the fair value of these awards prior to the IPO and we will continue to amortize the fair value thereof as follows for all pre-IPO equity grants: We measure the fair value of share options as of the grant date if equity treatment is applied, using the Black-Scholes option pricing model. The valuation model incorporates various assumptions including expected volatility of equity, expected term and risk-free interest rates. As we do not have a trading history for our Class A shares prior to the IPO, the expected share price volatility for our Class A shares prior to the IPO was estimated by taking the average historic price volatility for industry peers based on daily price observations over a period commensurate to the expected term. We base our expected term assumptions on the terms and conditions of the employee share option agreements, and scheduled exercise windows. Prior to the IPO, the share price assumption used in the model is based upon a valuation of trivago’s shares as of the grant date utilizing a blended analysis of the present value of future discounted cash flows and a market valuation approach. We amortize the fair value to the extent the awards qualify for equity treatment, over the vesting term on a straight-line basis. The majority of our share options vest between one and three years and have contractual terms that align with prescribed liquidation windows. We classify certain employee option awards as liabilities when we deem it not probable that the employees holding the awards will bear the risk and rewards of stock ownership for a reasonable period of time. We remeasure these instruments at fair value at the end of each reporting period using a Black-Scholes option pricing model which relies upon an estimate of the fair value of trivago’s shares as of the reporting date which is determined using a blended approach as discussed above. Upon settlement of these awards, our total share-based compensation expense recorded from grant date to settlement date will equal the settlement amount. We recognize the effect of forfeitures in the period that the award was forfeited.
Fair value recognition, measurement and disclosure	Fair value recognition, measurement and disclosure The carrying amounts of cash and restricted cash reported on our consolidated balance sheets approximate fair value as we maintain them with various high-quality financial institutions. The accounts receivable are short-term in nature and are generally settled shortly after the sale. We disclose the fair value of our financial instruments based on the fair value hierarchy using the following three categories: Level 1 - Valuations based on quoted prices for identical assets and liabilities in active markets. Level 2 - Valuations based on observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets and liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data. Level 3 - Valuations based on unobservable inputs reflecting the Company’s own assumptions, consistent with reasonably available assumptions made by other market participants. These valuations require significant judgment.
Certain risks and concentration of credit risk	Certain risks and concentration of credit risk Our business is subject to certain risks and concentrations including dependence on relationships with advertisers, dependence on third-party technology providers, and exposure to risks associated with online commerce security. Our concentration of credit risk relates to depositors holding the Company's cash and customers with significant accounts receivable balances. Our customer base includes primarily online travel agencies and hoteliers. We perform ongoing credit evaluations of our customers and maintain allowances for potential credit losses. We generally do not require collateral or other security from our customers.
Contingent liabilities	Contingent liabilities We have no material legal matters as of December 31, 2015 or 2016, as discussed further in Note 15 - Commitments and Contingencies. Periodically, we review the status of all significant outstanding matters to assess the potential financial exposure. When (i) it is probable that an asset has been impaired or a liability has been incurred and (ii) the amount of the loss can be reasonably estimated, we record the estimated loss in our consolidated statements of operations. We provide disclosure in the notes to the consolidated financial statements for loss contingencies that do not meet both of these conditions if there is a reasonable possibility that a loss may have been incurred that would be material to the financial statements. Significant judgment is required to determine the probability that a liability has been incurred and whether such liability is reasonably estimable. We base accruals made on the best information available at the time, which can be highly subjective. The final outcome of these matters could vary significantly from the amounts included in the accompanying consolidated financial statements. See Note 15 - Commitments and Contingencies.
Adoption of new accounting pronouncements and Recent accounting policies not yet adopted	Adoption of new accounting pronouncements In March 2016, the FASB issued new guidance related to accounting for share-based payments. The updated guidance changes how companies account for certain aspects of share-based payments awards to employees, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. The guidance is effective for annual and interim reporting periods beginning after December 15, 2016, with early adoption permitted. The adoption of this new guidance did not have a material impact to our consolidated financial statements. Recent accounting policies not yet adopted In May 2014, the FASB issued an ASU amending revenue recognition guidance and requiring more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. In August 2015, the FASB issued an ASU deferring the effective date of the revenue standard so it would be effective for annual and interim reporting periods beginning after December 15, 2017, with early adoption prohibited for accounting periods beginning before December 15, 2016. We expect to have our preliminary evaluation, including the selection of an adoption method, completed by the end of the first half of 2017. We are not planning on early adopting and currently expect to adopt the new revenue recognition guidance in the first quarter of 2018. In January 2016, the FASB issued new guidance related to accounting for equity investments, financial liabilities under the fair value option, and the presentation and disclosure requirements for financial instruments. In addition, the FASB clarified guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities. The new standard is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017. We are in the process of evaluating the impact of adopting this new guidance on our consolidated financial statements. In February 2016, the FASB issued new guidance related to accounting and reporting guidelines for leasing arrangements. The new guidance requires entities that lease assets to recognize assets and liabilities on the balance sheet related to the rights and obligations created by those leases regardless of whether they are classified as finance or operating leases. Consistent with current guidance, the recognition, measurement, and presentation of expenses and cash flows arising from a lease primarily will depend on its classification as a finance or operating lease. The guidance also requires new disclosures to help financial statement users better understand the amount, timing and uncertainty of cash flows arising from leases. This guidance is effective for annual and interim reporting periods beginning after December 15, 2018. Early adoption is permitted and should be applied using a modified retrospective approach. We are in the process of evaluating the impact of adopting this new guidance on our consolidated financial statements. In August and November 2016, the FASB issued new guidance related to the statement of cash flows which clarifies how companies present and classify certain cash receipts and cash payments as well as amends current guidance to address the classification and presentation of changes in restricted cash in the statement of cash flows. The new guidance is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017 with early adoption permitted. We are in the process of evaluating the impact of adopting this new guidance on our consolidated financial statements. In January 2017, the FASB issued new guidance clarifying the definition of a business for determining whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The new standard is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017 with early adoption permitted for transactions that occurred before the issuance date or effective date of the standard if the transactions were not reported in financial statements that have been issued or made available for issuance. We are in the process of evaluating the impact of adopting this new guidance on our consolidated financial statements. In January 2017, the FASB issued new guidance simplifying subsequent goodwill measurement by eliminating Step 2 from the goodwill impairment test. Under this update, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. The new standard is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2019 with early adoption permitted for annual goodwill impairment tests performed after January 1, 2017. The standard must be applied prospectively. We are in the process of evaluating the impact of adopting this new guidance on our consolidated financial statements.

Acquisitions (Tables)

12 Months Ended

Dec. 31, 2016

Business Combinations [Abstract]

The purchase price from our acquisitions was allocated to the fair value of assets acquired and liabilities assumed in the respective years as follows:



	Year ended December 31,
(in thousands)	2014			2015
Goodwill		€	859		€	2,583
Identifiable intangible assets:
Customer relationships		0			38
Net assets acquired⁽¹⁾		180			2,224
Redeemable noncontrolling interest		0			(2,230		)
Total purchase consideration		€	1,039		€	2,615

⁽¹⁾ Includes cash acquired of €0.1 million and €2.4 million in 2014 and 2015, respectively.

Business acquisition pro forma information

Supplemental information on an unaudited combined pro forma basis, as if the acquisitions had been consummated on January 1, 2014, is presented as follows:



	Year ended December 31,
(in thousands)	2014				2015
Revenue		€	311,076			€	494,387
Net loss		€	(22,973	)		€	(39,359	)

Fair value measurement (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Fair value measurement on recurring basis

The redeemable noncontrolling interest is measured at fair value on a recurring basis as of December 31, 2015 and 2016 and classified using the fair value hierarchy in the tables below:



		December 31, 2015
(in thousands)	Total			Level 1			Level 2			Level 3
Redeemable noncontrolling interest:
Put/call option		€	2,076		€	0		€	0		€	2,076
Total mezzanine equity		€	2,076		€	0		€	0		€	2,076



	December 31, 2016
(in thousands)	Total			Level 1			Level 2			Level 3
Redeemable noncontrolling interest:
Put/call option		€	351		€	0		€	0		€	351
Total mezzanine equity		€	351		€	0		€	0		€	351

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

Property, Plant and Equipment [Abstract]

Property and equipment, net (Tables)

12 Months Ended

Dec. 31, 2016

Schedule of property and equipment, net



	As of December 31,
(in thousands)	2015			2016
Capitalized software and software development costs		€	4,517	€	7,302
Computer equipment		5,186		8,358
Furniture and fixtures		1,963		2,743
Office equipment		394		1,009
Leasehold improvements		964		1,811
Subtotal		13,024		21,223
Less: accumulated depreciation		5,024		10,096
Construction in process		4,853		35,735
Property and equipment, net		€	12,853	€	46,862

Goodwill and intangible assets, net (Tables)

12 Months Ended

Dec. 31, 2016

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of goodwill and intangible assets

The following table presents our goodwill and intangible assets as of December 31, 2015 and 2016:



	As of December 31,
(in thousands)		2015			2016
Goodwill			€	490,360		€	490,503
Intangible assets with definite lives, net			20,409			6,552
Intangible assets with indefinite lives			169,500			169,500
Total			€	680,269		€	666,555

Schedule of goodwill

The following table presents the changes in goodwill by reporting segment:



(in thousands)	Developed Europe				Americas				Rest of World				Total
Balance as of January 1, 2015		€	214,152			€	191,718			€	82,084			€	487,954
Additions		1,134				1,015				434				2,583
Foreign exchange translation		(78		)		(70		)		(29		)		(177		)
Balance as of December 31, 2015		215,208				192,663				82,489				490,360
Foreign exchange translation		63				56				24				143
Balance as of December 31, 2016		€	215,271			€	192,719			€	82,513			€	490,503

Components of intangible assets with definite lives

The following table presents the components of our intangible assets with definite lives as of December 31, 2015 and 2016:



(in thousands)		December 31, 2015									December 31, 2016
	Cost			(Accumulated Amortization)				Net			Cost			(Accumulated Amortization)				Net
Customer relationships		€	38		€	(5	)		€	33		€	38		€	(15	)		€	23
Partner relationships		34,220			(24,055		)		10,165			34,220			(32,610		)		1,610
Technology		59,780			(56,030		)		3,750			59,780			(59,780		)		—
Non-compete agreement		10,800			(4,339		)		6,461			10,800			(5,881		)		4,919
Total		€	104,838		€	(84,429	)		€	20,409		€	104,838		€	(98,286	)		€	6,552

Schedule of definite lives intangible assets, future amortization expense

The estimated future amortization expense related to intangible assets with definite lives as of December 31, 2016, assuming no subsequent impairment of the underlying assets, is as follows:



(in thousands)	Amortization
2017		€	3,163
2018		1,553
2019		1,546
2020		290
Total		€	6,552

Share-based awards and other equity instruments (Tables)

12 Months Ended

Dec. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of stock options activity

The following table presents a summary of our share option activity in trivago N.V. equivalent shares:



	As of December 31, 2016
	Options	Weighted average exercise price			Remaining contractual life		Aggregate intrinsic value
						(In years)
Balance as of January 1, 2014	887		€	1
Granted	180		€	9,974
Balance as of December 31, 2014	1,067		€	1,683
Granted	139		€	3,871
Exercised	484		€	1
Balance as of December 31, 2015	722		€	3,239
Granted	221		€	80,926
Exercised	39		€	17,953
Cancelled	2		€	1
Balance as of December 31, 2016	902		€	21,637		0.77		€	68,235
Balance as of December 31, 2016 (trivago N.V. equivalents)	7,704,659
Exercisable as of December 31, 2016	517		€	209		0.77		€	89,663
Vested and expected to vest after December 31, 2016	902		€	21,637		0.77		€	68,235

Schedule of stock options valuation assumptions

The fair value of share options granted during the years ended December 31, 2014, 2015 and 2016 were estimated at the date of grant using the Black-Scholes option-pricing model, assuming the following weighted average assumptions:



	Year ended December 31,
	2014				2015			2016
Risk-free interest rate		1.31		%	1.31		%		1.31		%
Expected volatility		46		%	46		%		46		%
Expected life (in years)		2.98			1.82				2.68
Dividend yield		—		%	—		%		—		%
Weighted-average estimated fair value of options granted during the year		€	22,689		€	29,496			€	34,425

Income taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Schedule of components of income tax expense/(benefit)

The following table summarizes our income tax expense/(benefit):



	Year ended December 31,
(in thousands)	2014				2015				2016
Current income tax expense (benefit):
Germany		€	628			€	(1,032	)	€	11,405
Other countries		43				158			103
Current income tax expense (benefit)		671				(874		)	11,508
Deferred income tax (benefit) expense:
Germany		(9,315		)		(10,444		)	(4,838		)
Other countries		—				—			—
Deferred income tax (benefit) expense		(9,315		)		(10,444		)	(4,838		)
Income tax expense (benefit)		€	(8,644	)		€	(11,318	)	€	6,670

Schedule of income (loss) before income tax, domestic and foreign

The following table summarizes our income (loss) before income taxes allocated to Germany and to other countries:



	Year ended December 31,
(in thousands)	2014				2015				2016
Germany		€	(32,033	)		€	(50,446	)		€	(32,985	)
Other countries		293				(238		)		(11,736		)
Income (loss) before income taxes		€	(31,740	)		€	(50,684	)		€	(44,721	)

Schedule of effective income tax rate reconciliation

A reconciliation of amounts computed by applying the German statutory income tax rate to income from continuing operations before income taxes to total income tax expense (benefit) is as follows:



	Year ended December 31,
(in thousands)	2014				2015				2016
Income (loss) before income taxes		€	(31,740	)		€	(50,684	)		€	(44,721	)
Income tax expense at German tax rate (31.23%)		(9,912		)		(15,829		)		(13,964		)
Foreign rate differential		(11		)		34				219
Expected tax expense (benefit)		(9,923		)		(15,795		)		(13,745		)
Tax effect from:
Non-deductible share-based compensation		744				4,409				16,875
Non-deductible corporate costs		470				882				1,306
Changes in uncertain tax positions		—				(1,666		)		—
Movement in valuation allowance		—				98				1,921
Other differences		65				754				313
Income tax expense (benefit)		€	(8,644	)		€	(11,318	)		€	6,670

Summary of gross unrecognized tax benefits

A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows:



	Year Ended December 31,
(in thousands)	2014			2015				2016
Balance, beginning of year		€	1,545		€	1,666			€	—
Reductions due to lapsed statute of limitations during current year					(1,666		)		—
Interest and penalties		121			—				—
Balance, end of year		€	1,666		€	—			€	—

Schedule of deferred tax assets and liabilities

As of December 31, 2015 and 2016, the significant components of our deferred tax assets and deferred tax liabilities were as follows:



	Year Ended December 31,
(in thousands)	2015			2016
Deferred tax assets:
Prepaid expense and other current assets	€	683		€	1,285
Accounts payable, other	456			5
Net operating loss and tax credit carryforwards	110			3,566
Other	750			1,331
Total deferred tax assets	1,998			6,187
Less valuation allowance	(98		)	(3,550		)
Net deferred tax assets	1,900			2,637
Deferred tax liabilities:
Intangible assets, net	59,301			54,972
Property and equipment	594			812
Other	—			9
Total deferred tax liabilities	59,894			55,793
Net deferred tax asset/(liability)	€	(57,994	)	€	(53,156	)

Redeemable noncontrolling interests (Tables)

12 Months Ended

Dec. 31, 2016

Noncontrolling Interest [Abstract]

Reconciliation of redeemable noncontrolling interest

A reconciliation of redeemable noncontrolling interest for the years ended December 31, 2015 and December 31, 2016 is as follows:



	Year ended December 31,
(in thousands)	2015				2016
Balance, beginning of the period		€	0			€	2,076
Acquisition of redeemable noncontrolling interests		2,230				0
Net loss attributable to noncontrolling interests		(239		)		(995		)
Fair value adjustments through members’ equity		239				995
Currency translation adjustments and other		(154		)		129
Change in ownership of noncontrolling interest		—				€	(1,854	)
Balance, end of period		€	2,076			€	351

Commitments and contingencies (Tables)

12 Months Ended

Dec. 31, 2016

Commitments and Contingencies Disclosure [Abstract]

Long-term purchase commitment

Commitments and obligations as of December 31, 2016 were as follows:



	By Period
(in thousands)	Total			Less than 1 year			1 to 3 years			3 to 5 years			More than 5 years
Purchase obligations		€	40,374		€	31,374		€	9,000		€	—		€	—

Schedule of estimated future minimum rental payments under operating leases

The following table presents our estimated future minimum rental payments under operating leases with noncancelable lease terms that expire after December 31, 2016:



(in thousands)	Year ending December 31,
2017		€	4,035
2018		6,367
2019		8,324
2020		6,799
2021		6,799
2022 and thereafter		38,433
Total		€	70,757

Segment information (Tables)

12 Months Ended

Dec. 31, 2016

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment



	Year Ended December 31, 2014
(in thousands)	Developed Europe			Americas				Rest of World				Corporate & Eliminations			Total
Referral revenue		€	210,241		€	73,316			€	25,595			€	0		€	309,152
Other revenue		0			0				0				180			180
Total revenue		210,241			73,316				25,595				180			309,332
Advertising spend		162,358			81,110				27,899				0			271,367
ROAS contribution		€	47,883		€	(7,794	)		€	(2,304	)		€	180		€	37,965
Costs and expenses:
Cost of revenue, including related party, excluding amortization																1,443
Other selling and marketing⁽¹⁾																14,867
Technology and content																15,388
General and administrative, including related party shared service fee																6,536
Amortization of intangible assets																30,025
Operating income (loss)																(30,294		)
Other income (expense)
Interest expense																(11		)
Other, net																(1,435		)
Total other income (expense), net																(1,446		)
Income (loss) before income taxes																(31,740		)
Provision for income taxes																(8,644		)
Net loss																€	(23,096	)

(1) Represents all other sales and marketing, excluding advertising spend, as advertising spend is tracked by reporting segment.



	Year Ended December 31, 2015
(in thousands)	Developed Europe			Americas			Rest of World				Corporate & Eliminations			Total
Referral revenue		€	259,568		€	171,910		€	58,762			€	0		€	490,240
Other revenue		0			0			0				2,843			2,843
Total revenue		259,568			171,910			58,762				2,843			493,083
Advertising spend		194,886			169,415			67,872				0			432,173
ROAS contribution		€	64,682		€	2,495		€	(9,110	)		€	2,843		€	60,910
Costs and expenses:
Cost of revenue, including related party, excluding amortization															2,946
Other selling and marketing⁽¹⁾															29,046
Technology and content															28,693
General and administrative, including related party shared service fee															18,065
Amortization of intangible assets															30,030
Operating income (loss)															(47,870		)
Other income (expense)
Interest expense															(147		)
Other, net															(2,667		)
Total other income (expense), net															(2,814		)
Income (loss) before income taxes															(50,684		)
Provision for income taxes															(11,318		)
Net loss															€	(39,366	)

(1) Represents all other sales and marketing, excluding advertising spend, as advertising spend is tracked by reporting segment.



	Year Ended December 31, 2016
(in thousands)	Developed Europe			Americas			Rest of World				Corporate & Eliminations			Total
Referral revenue		€	348,909		€	286,398		€	110,517			€	0		€	745,824
Other revenue		0			0			0				8,345			8,345
Total revenue		348,909			286,398			110,517				8,345			754,169
Advertising spend		257,471			243,176			122,805				0			623,452
ROAS contribution		€	91,438		€	43,222		€	(12,288	)		€	8,345		€	130,717
Costs and expenses:
Cost of revenue, including related party, excluding amortization															4,273
Other selling and marketing(1)															51,277
Technology and content															51,658
General and administrative, including related party shared service fee															54,097
Amortization of intangible assets															13,857
Operating income (loss)															(44,445		)
Other income (expense)
Interest expense															(137		)
Other, net															(139		)
Total other income (expense), net															(276		)
Income (loss) before income taxes															(44,721		)
Provision for income taxes															6,670
Net loss															€	(51,391	)

(1) Represents all other sales and marketing, excluding advertising spend, as advertising spend is tracked by reporting segment.

Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas



	Year ended December 31,
(in thousands)	2014			2015			2016
Total Revenues
United States		€	54,560		€	128,891		€	199,423
Germany		57,826			67,470			76,599
United Kingdom		46,707			61,541			86,745
Spain		25,776			29,206			37,715
Italy		23,197			26,394			31,272
Canada		15,422			23,156			33,112
All other countries		85,844			156,425			289,303
		€	309,332		€	493,083		€	754,169

The following table presents property and equipment, net for Germany and all other countries, as of December 31, 2015 and 2016:



(in thousands)		Years ended December 31,
	2015			2016
Property and equipment, net
Germany		€	12,676		€	46,098
All other countries		177			764
		€	12,853		€	46,862

Valuation and qualifying accounts (Tables)

12 Months Ended

Dec. 31, 2016

Valuation and Qualifying Accounts [Abstract]

Schedule of valuation and qualifying accounts

The following table presents the changes in our valuation and qualifying accounts not disclosed elsewhere in these financial statements.



(in thousands)	Balance at Beginning of Period		Charges to Earnings		Deductions			Balance at End of Period
2014
Allowance for doubtful accounts	€	253	€	624	€	(216	)	€	661
2015
Allowance for doubtful accounts	661		241		(651		)	€	251
2016
Allowance for doubtful accounts	€	251	€	1,749	€	(1,848	)	€	152

Organization and basis of presentation (Details) € / shares in Units, € in Millions	1 Months Ended
	Dec. 31, 2016 EUR (€) € / shares shares	Dec. 31, 2016 $ / shares	Nov. 30, 2016 shares	Nov. 06, 2016	Jun. 30, 2016
Subsidiary, Sale of Stock [Line Items]
Ownership percentage by parent	68.30%	68.30%
Ownership percentage by noncontrolling owners	31.70%	31.70%
Class A Common Stock
Subsidiary, Sale of Stock [Line Items]
Class common stock, par value (in EUR per ADS) \| € / shares	€ 0.06
Number of shares contributed by the Founders (in shares)			9,200,029
IPO \| Class A Common Stock
Subsidiary, Sale of Stock [Line Items]
Sale of Stock, Number of Shares Issued in Transaction	20,826,606
Number of common stock per ADS	1
Class common stock, par value (in EUR per ADS) \| € / shares	€ 0.06
Public offering price (in USD per ADS) \| $ / shares		$ 11.00
Net offering proceeds from issuance initial public offering \| €	€ 207.8
Expedia
Subsidiary, Sale of Stock [Line Items]
Ownership percentage by parent	87.40%	87.40%	96.30%	63.50%	63.50%
Voting ownership by shareholders			99.60%
Voting power percentage by parent	98.60%	98.60%
Indirect ownership percentage by Parent	59.70%	59.70%
Indirect voting power percentage by Parent	64.70%	64.70%
Travel B.V.
Subsidiary, Sale of Stock [Line Items]
Voting power percentage by parent			66.00%
Voting power percentage by noncontrolling owners			34.00%
Trivago GmbH
Subsidiary, Sale of Stock [Line Items]
Number of shares contributed by the Founders (in shares)			940
Number of shares contributed by the Founders, percentage			6.70%
Messrs. Schrömgens, Vinnemeier and Siewert
Subsidiary, Sale of Stock [Line Items]
Ownership percentage by noncontrolling owners				36.50%
Voting ownership by shareholders			0.40%
Ownership by shareholders			3.70%

Significant accounting policies (Details) € in Thousands	6 Months Ended	12 Months Ended
Significant accounting policies (Details) € in Thousands	Dec. 31, 2016 EUR (€) segment	Dec. 31, 2016 EUR (€) reporting_unit segment	Dec. 31, 2015 EUR (€)	Dec. 31, 2014 EUR (€)	Jul. 31, 2015 m²
Significant Accounting Policies [Line Items]
Ownership percentage by noncontrolling owners	31.70%	31.70%
Amortization of intangible assets		€ 13,857	€ 30,030	€ 30,025
Land rent expense		€ 1,700	900
Number of reporting units \| reporting_unit		3
Number of operating segments \| segment	3	3
Advertising spend		€ 623,452	432,173	271,367
Prepaid marketing expenses	€ 3,400	€ 3,400	€ 3,800	€ 4,500
Minimum
Significant Accounting Policies [Line Items]
Property and equipment useful life		3 years
Maximum
Significant Accounting Policies [Line Items]
Property and equipment useful life		5 years
Intangible asset, useful life		7 years
Software Development Costs
Significant Accounting Policies [Line Items]
Property and equipment useful life		3 years
Software Enhancement Costs
Significant Accounting Policies [Line Items]
Property and equipment useful life		3 years
Expedia \| Customer Concentration Risk \| Revenue
Significant Accounting Policies [Line Items]
Concentration risk, percentage		36.00%	39.00%	32.00%
Expedia \| Customer Concentration Risk \| Accounts Receivable
Significant Accounting Policies [Line Items]
Concentration risk, percentage		31.00%	55.00%
Priceline.com \| Customer Concentration Risk \| Revenue
Significant Accounting Policies [Line Items]
Concentration risk, percentage		43.00%	27.00%	28.00%
Priceline.com \| Customer Concentration Risk \| Accounts Receivable
Significant Accounting Policies [Line Items]
Concentration risk, percentage		48.00%	21.00%
Düsseldorf, Germany \| Office building
Significant Accounting Policies [Line Items]
Lease area \| m²					26,107
Acquired technology
Significant Accounting Policies [Line Items]
Amortization of intangible assets		€ 3,750	€ 19,927	€ 19,927
Internal use software and website development costs
Significant Accounting Policies [Line Items]
Amortization of intangible assets		€ 1,410	€ 475	€ 191

Acquisitions (Details) € in Thousands					6 Months Ended	12 Months Ended
Acquisitions (Details) € in Thousands	Dec. 22, 2016 EUR (€)	Aug. 05, 2015 EUR (€)	Jul. 16, 2015 EUR (€)	Dec. 19, 2014 EUR (€)	Dec. 31, 2016 EUR (€) segment	Dec. 31, 2016 EUR (€) segment	Dec. 31, 2015 EUR (€)	Dec. 31, 2014 EUR (€)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill					€ 490,503	€ 490,503	€ 490,360	€ 487,954
Identifiable intangible assets:
Cash acquired							2,400	100
Acquisition-related costs							800	200
Number of operating segments \| segment					3	3
Business Acquisition, Pro Forma Information [Abstract]
Revenue							494,387	311,076
Net loss							(39,359)	(22,973)
Rheinfabrik, Myhotelshop NV, And Base7booking Acquisitions
Business Acquisition [Line Items]
Total purchase consideration							2,615	1,039
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill							2,583	859
Identifiable intangible assets:
Customer relationships							38	0
Net assets acquired							2,224	180
Redeemable noncontrolling interest							(2,230)	€ 0
Rheinfabrik
Business Acquisition [Line Items]
Percentage of equity interest acquired				100.00%
Total purchase consideration				€ 1,000
Base7 and Myhotelshop
Identifiable intangible assets:
Redeemable noncontrolling interest							(2,200)
Revenue of acquiree							1,400
Operating losses of acquiree							€ 500
Myhotelshop N.V.
Business Acquisition [Line Items]
Percentage of equity interest acquired			61.30%
Total purchase consideration			€ 600
Base7booking.com
Business Acquisition [Line Items]
Percentage of equity interest acquired	47.70%	52.30%
Total purchase consideration		€ 2,100
Business Acquisition, Pro Forma Information [Abstract]
Payments to acquire businesses	€ 900

Fair value measurement (Details) - EUR (€)	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility, fair value	€ 0
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Redeemable noncontrolling interest, fair value	351,000	€ 2,076,000
Recurring \| Put/call option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Redeemable noncontrolling interest, fair value	351,000	2,076,000
Recurring \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Redeemable noncontrolling interest, fair value	0	0
Recurring \| Level 1 \| Put/call option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Redeemable noncontrolling interest, fair value	0	0
Recurring \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Redeemable noncontrolling interest, fair value	0	0
Recurring \| Level 2 \| Put/call option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Redeemable noncontrolling interest, fair value	0	0
Recurring \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Redeemable noncontrolling interest, fair value	351,000	2,076,000
Recurring \| Level 3 \| Put/call option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Redeemable noncontrolling interest, fair value	€ 351,000	€ 2,076,000

Property and equipment, net (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment, gross	€ 21,223	€ 13,024
Less: accumulated depreciation	10,096	5,024
Property and equipment, net	46,862	12,853
Amortization of capitalized software development costs	1,200	500	€ 200
Capitalized software and software development costs
Property, Plant and Equipment [Line Items]
Property and equipment, gross	7,302	4,517
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	8,358	5,186
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,743	1,963
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,009	394
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,811	964
Construction in process
Property, Plant and Equipment [Line Items]
Property and equipment, gross	35,735	4,853
Software Development Costs
Property, Plant and Equipment [Line Items]
Property and equipment, gross	€ 2,600	€ 1,900

Goodwill and intangible assets, net (Details) - EUR (€)	12 Months Ended
Goodwill and intangible assets, net (Details) - EUR (€)	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Goodwill	€ 490,360,000	€ 487,954,000	€ 487,954,000	€ 490,503,000	€ 490,360,000
Intangible assets with definite lives, net				6,552,000	20,409,000
Intangible assets with indefinite lives				169,500,000	169,500,000
Total				666,555,000	680,269,000
Accumulated impairment losses of goodwill				0	0
Accumulated impairment losses of indefinite-lived intangible assets	0	0
Goodwill [Roll Forward]
Goodwill, Beginning Balance	490,360,000	487,954,000
Additions		2,583,000
Foreign exchange translation	143,000	(177,000)
Goodwill, Ending Balance	490,503,000	490,360,000	487,954,000
Finite-Lived Intangible Assets, Net [Abstract]
Intangible assets with definite lives, Cost				104,838,000	104,838,000
Intangible assets with definite lives, Accumulated Amortization				(98,286,000)	(84,429,000)
Amortization of intangible assets	13,857,000	30,030,000	30,025,000
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2017				3,163,000
2018				1,553,000
2019				1,546,000
2020				290,000
Developed Europe
Finite-Lived Intangible Assets [Line Items]
Goodwill	215,208,000	214,152,000	214,152,000	215,271,000	215,208,000
Goodwill [Roll Forward]
Goodwill, Beginning Balance	215,208,000	214,152,000
Additions		1,134,000
Foreign exchange translation	63,000	(78,000)
Goodwill, Ending Balance	215,271,000	215,208,000	214,152,000
Americas
Finite-Lived Intangible Assets [Line Items]
Goodwill	192,663,000	191,718,000	191,718,000	192,719,000	192,663,000
Goodwill [Roll Forward]
Goodwill, Beginning Balance	192,663,000	191,718,000
Additions		1,015,000
Foreign exchange translation	56,000	(70,000)
Goodwill, Ending Balance	192,719,000	192,663,000	191,718,000
Rest of World
Finite-Lived Intangible Assets [Line Items]
Goodwill	82,489,000	82,084,000	82,084,000	82,513,000	82,489,000
Goodwill [Roll Forward]
Goodwill, Beginning Balance	82,489,000	82,084,000
Additions		434,000
Foreign exchange translation	24,000	(29,000)
Goodwill, Ending Balance	€ 82,513,000	€ 82,489,000	€ 82,084,000
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets with definite lives, net				23,000	33,000
Finite-Lived Intangible Assets, Net [Abstract]
Intangible assets with definite lives, Cost				38,000	38,000
Intangible assets with definite lives, Accumulated Amortization				(15,000)	(5,000)
Partner relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets with definite lives, net				1,610,000	10,165,000
Finite-Lived Intangible Assets, Net [Abstract]
Intangible assets with definite lives, Cost				34,220,000	34,220,000
Intangible assets with definite lives, Accumulated Amortization				(32,610,000)	(24,055,000)
Technology
Finite-Lived Intangible Assets [Line Items]
Intangible assets with definite lives, net				0	3,750,000
Finite-Lived Intangible Assets, Net [Abstract]
Intangible assets with definite lives, Cost				59,780,000	59,780,000
Intangible assets with definite lives, Accumulated Amortization				(59,780,000)	(56,030,000)
Non-compete agreement
Finite-Lived Intangible Assets [Line Items]
Intangible assets with definite lives, net				4,919,000	6,461,000
Finite-Lived Intangible Assets, Net [Abstract]
Intangible assets with definite lives, Cost				10,800,000	10,800,000
Intangible assets with definite lives, Accumulated Amortization				€ (5,881,000)	€ (4,339,000)

Debt - credit facility (Details) - EUR (€)	12 Months Ended
Debt - credit facility (Details) - EUR (€)	Dec. 31, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Short-term debt	€ 0	€ 20,000,000
Uncommitted Credit Facility
Line of Credit Facility [Line Items]
Uncommitted credit facility principle amount	€ 50,000,000
LIBOR \| Uncommitted Credit Facility
Line of Credit Facility [Line Items]
Debt basis spread on variable rate	1.00%

Share-based awards and other equity instruments - Narrative (Details)	3 Months Ended			12 Months Ended
	Sep. 30, 2016 EUR (€) shares	Jun. 30, 2016 EUR (€)	Sep. 30, 2015 EUR (€) shares	Dec. 31, 2016 EUR (€) € / shares shares	Dec. 31, 2015 EUR (€) € / shares shares	Dec. 31, 2014 EUR (€) € / shares shares	Dec. 31, 2013 € / shares shares	Nov. 30, 2016 shares	Nov. 06, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, conversion ratio				0.001	0.001
Related party payable				€ 0	€ 7,129,000
One-time modification charge due to classification of awards from equity to liability accounting treatment			€ 7,300,000
Contribution from Parent		€ 62,500,000		122,200,000	55,529,000
Share-based compensation		43,700,000		€ 53,700,000	14,100,000	€ 2,400,000
Loans receivable from shareholders		7,100,000
Ownership percentage by parent				68.30%
Reclassification of option liability to reserves	€ 4,200,000			€ 4,893,000
Proceeds from exercise of option awards	€ 700,000			685,000	0	0
Intrinsic value of shares exercised				€ 3,000,000	16,200,000
Number of options subject to liability accounting (in shares) \| shares				0
Income tax benefit related to share-based compensation expense				€ 0	0	0
Capitalized share-based compensation cost				318,000	103,000	8,000
Cash received from share-based award exercises				685,000	€ 10,000	€ 0
Unrecognized share-based compensation expense				€ 9,300,000
Unrecognized share-based compensation expense, period for recognition (less than)				1 year
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Strike price for majority of options (in EUR per share) \| € / shares				€ 1	€ 1	€ 1	€ 1
Stock Option \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)				2 years	2 years	2 years	1 year
Stock Option \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)				3 years	3 years	3 years	3 years
Trivago amended option plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options outstanding (in shares) \| shares				902	722	1,067	887
Number of replacement awards at acquisition (in shares) \| shares							858
Granted (in shares) \| shares				221	139	180
Exercised (in share) \| shares				39	484
Reclassification of option liability to reserves				€ 4,900,000
Trivago amended option plan \| Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Strike price for majority of options (in EUR per share) \| € / shares				€ 1
2016 Omnibus Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares) \| shares				0
Number of shares available for grant \| shares				34,711,009
Number of supervisory board in plan administration committee				2
Share-based payment award, term				10 years
2016 Omnibus Incentive Plan \| Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment award, term				10 years
2016 Omnibus Incentive Plan \| Share Appreciation Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment award, term				10 years
Expedia \| Principal owner
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Related party payable		€ 7,100,000	€ 7,100,000		€ 7,100,000
Expedia
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ownership percentage by parent		63.50%		87.40%				96.30%	63.50%
Class A Common Stock \| Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares) \| shares				146	77	180
Exercised (in share) \| shares	38		484
Number of options subject to liability accounting (in shares) \| shares					130	100		93
Class B Common Stock \| Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares) \| shares				74,580	62,178
Number of options subject to liability accounting (in shares) \| shares					7			6

Share-based awards and other equity instruments - Stock options activities (Details) - Trivago amended option plan - EUR (€) € / shares in Units, € in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance (in shares)	722	1,067	887
Granted (in shares)	221	139	180
Exercised (in share)	39	484
Canceled (in shares)	2
Ending balance (in shares)	902	722	1,067
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning balance, Weighted average exercise price (in EUR per share)	€ 3,239	€ 1,683	€ 1
Granted, Weighted average exercise price (in EUR per share)	80,926	3,871	9,974
Exercised, Weighted average exercise price (in EUR per share)	17,953	1
Canceled, Weighted average exercise price (in EUR per share)	1
Ending balance, Weighted average exercise price (in EUR per share)	€ 21,637	€ 3,239	€ 1,683
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Outstanding, Remaining contractual term (in years)	9 months 8 days
Exercisable (in shares)	517
Exercisable, Weighted average exercise price (in EUR per share)	€ 209
Exercisable, Remaining contractual term (in years)	9 months 8 days
Exercisable, Aggregate intrinsic value	€ 89,663
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest [Abstract]
Vested and expected to vest (in shares)	902
Vested and expected to vest, Weighted average exercise price (in EUR per share)	€ 21,637
Vested and expected to vest after, Remaining contractual life (in years)	9 months 8 days
Vested and expected to vest after, Aggregate intrinsic value	€ 68,235
Trivago N.V.
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance (in shares)
Ending balance (in shares)	7,704,659

Share-based awards and other equity instruments - Stock options fair value assumptions (Details) - € / shares € / shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Risk-free interest rate	1.31%	1.31%	1.31%
Expected volatility	46.00%	46.00%	46.00%
Expected life (in years)	2 years 8 months 6 days	1 year 9 months 24 days	2 years 11 months 24 days
Dividend yield	0.00%	0.00%	0.00%
Weighted-average estimated fair value of options granted during the year (in EUR per share)	€ 34,425	€ 29,496	€ 22,689

Income taxes - Schedule of income tax expenses/(benefit) (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current income tax expense (benefit):
Germany	€ 11,405	€ (1,032)	€ 628
Other countries	103	158	43
Current income tax expense (benefit)	11,508	(874)	671
Deferred income tax (benefit) expense:
Germany	(4,838)	(10,444)	(9,315)
Other countries	0	0	0
Deferred income tax (benefit) expense	(4,838)	(10,444)	(9,315)
Income tax expense (benefit)	€ 6,670	€ (11,318)	€ (8,644)

Income taxes - Reconciliation of German statutory income tax rate to effective income tax rate (Details) - EUR (€) € in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest [Abstract]
Germany		€ (32,985)	€ (50,446)	€ (32,033)
Other countries		(11,736)	(238)	293
Income (loss) before income taxes		(44,721)	(50,684)	(31,740)
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax expense at German tax rate (31.23%)		(13,964)	(15,829)	(9,912)
Foreign rate differential		219	34	(11)
Expected tax expense (benefit)		(13,745)	(15,795)	(9,923)
Tax effect from:
Non-deductible share-based compensation		16,875	4,409	744
Non-deductible corporate costs		1,306	882	470
Changes in uncertain tax positions		0	(1,666)	0
Movement in valuation allowance		1,921	98	0
Other differences		313	754	65
Income tax expense (benefit)		€ 6,670	€ (11,318)	€ (8,644)
German tax rate		31.23%	31.23%	31.23%
Effective tax rate		(14.90%)	22.30%	27.20%
Share-based compensation	€ 43,700	€ 53,700	€ 14,100	€ 2,400
Corporate costs pushed down from Parent		€ 4,185	2,826	€ 1,506
Non-tax deductible expense, release of contingent asset			520
Total non-tax deductible expense			€ 852

Income taxes - Uncertain Tax Positions (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance, beginning of year	€ 0	€ 1,666	€ 1,545
Reductions due to lapsed statute of limitations during current year	0	(1,666)
Interest and penalties	0	0	121
Balance, end of year	€ 0	€ 0	€ 1,666

Income taxes - Deferred Income Taxes (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Prepaid expense and other current assets	€ 1,285	€ 683
Accounts payable, other	5	456
Net operating loss and tax credit carryforwards	3,566	110
Other	1,331	750
Total deferred tax assets	6,187	1,998
Less valuation allowance	(3,550)	(98)
Net deferred tax assets	2,637	1,900
Deferred tax liabilities:
Intangible assets, net	54,972	59,301
Property and equipment	812	594
Other	9	0
Total deferred tax liabilities	55,793	59,894
Net deferred tax asset/(liability)	(53,156)	€ (57,994)
Net operating loss carryforwards	3,600
NOL carryforwards, valuation allowance	3,600
Increase in tax-effected valuation allowance	3,500
Increase in tax-effected valuation allowance, related to tax losses from IPO	1,600
Unrecognized tax benefits that would impact effective tax rate	3,600
Undistributed earnings of foreign subsidiaries (less than)	100
Trivago N.V.
Deferred tax liabilities:
Net operating loss carryforwards	3,200
Myhotelshop
Deferred tax liabilities:
Net operating loss carryforwards	€ 400

Redeemable noncontrolling interests (Details) - EUR (€) € in Thousands	1 Months Ended	11 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 15, 2016	Dec. 31, 2016	Dec. 31, 2015
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Balance, beginning of the period		€ 2,076	€ 2,076	€ 0
Acquisition of redeemable noncontrolling interests			0	2,230
Net loss attributable to noncontrolling interests	€ (43)	€ (952)	(995)	(239)
Fair value adjustments through members’ equity			995	239
Currency translation adjustments and other			129	(154)
Change in ownership of noncontrolling interest			(1,854)	0
Balance, end of period	€ 351		€ 351	€ 2,076

Stockholders'/members' equity (Details) € / shares in Units, € in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2016 EUR (€) € / shares shares	Dec. 31, 2016 voting_right € / shares shares	Dec. 31, 2015
Class of Stock [Line Items]
Common stock, conversion ratio		0.001	0.001
Class A Common Stock
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding	30,026,635	30,026,635
Class common stock, par value (in EUR per ADS) \| € / shares	€ 0.06	€ 0.06
Common stock, voting rights per share \| voting_right		1
Class B Common Stock
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding	209,008,088	209,008,088
Class common stock, par value (in EUR per ADS) \| € / shares	€ 0.60	€ 0.60
Common stock, voting rights per share \| voting_right		10
Trivago GmbH
Class of Stock [Line Items]
Common stock, conversion ratio		0.001
Common stock dividends \| €	€ 0.5
Payments of common stock dividends \| €	€ 0.2
Trivago GmbH \| Class A Common Stock
Class of Stock [Line Items]
Exchangeable shares, outstanding	110,791,880	110,791,880
Trivago N.V. \| Class B Common Stock
Class of Stock [Line Items]
Exchangeable shares, outstanding	110,791,880	110,791,880

Earnings per share (Details) - EUR (€)
€ / shares in Units, € in Thousands, shares in Thousands

1 Months Ended

12 Months Ended

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2014

Numerator:

Net income

€ 1,185

€ (51,391)

€ (39,366)

€ (23,096)

Less: net income attributable to noncontrolling interest

285

(710)

(239)

Net loss attributable to trivago N.V.

€ 900

€ (50,681)

€ (39,127)

€ (23,096)

Denominator:

Weighted average shares of Class A and Class B common stock outstanding - basic and diluted

237,811

Earnings per share attributable to trivago N.V. available to Class A and Class B common stockholders - basic and diluted (in EUR per share)

^[1]

€ 0.00

[1]	Represents earnings per share of Class A and Class B common stock and weighted-average shares of Class A and Class B common stock outstanding for the period from December 16, 2016 through December 31, 2016, the period following the capitalization of the parent company and IPO (see Note 13).

Other, net (Details) - EUR (€) € in Thousands	12 Months Ended
Other, net (Details) - EUR (€) € in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Income and Expenses [Abstract]
Foreign exchange rate gains (losses), net	€ 16	€ (1,006)	€ (1,558)
Indemnification asset and related interest	0	(1,661)	123
Other expenses	(155)	0	0
Total	€ (139)	€ (2,667)	€ (1,435)

Commitments and contingencies (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Purchase Obligation, Fiscal Year Maturity [Abstract]
Total	€ 40,374
Less than 1 year	31,374
1 to 3 years	9,000
3 to 5 years	0
More than 5 years	0
Rental expense	4,600	€ 3,300	€ 2,200
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2017	4,035
2018	6,367
2019	8,324
2020	6,799
2021	6,799
2022 and thereafter	38,433
Total	€ 70,757

Related party transactions (Details) - EUR (€)		12 Months Ended
Related party transactions (Details) - EUR (€)	Sep. 05, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jun. 30, 2016	Sep. 30, 2015	Dec. 19, 2014
Related Party Transaction [Line Items]
Revenue from related party		€ 268,227,000	€ 194,241,000	€ 100,195,000
Other operating expenses from related party		4,185,000	2,826,000	1,506,000
Accounts receivable, related party		16,505,000	23,605,000
Related party payable		0	7,129,000
Proceeds from issuance of credit facility		20,000,000	20,000,000	0
Repayments of debt		40,000,000	0	0
Proceeds from issuance of loan from related party		€ 0	€ 7,129,000	€ 1,039,000
Revenue \| Customer Concentration Risk \| Expedia
Related Party Transaction [Line Items]
Concentration risk, percentage		36.00%	39.00%	32.00%
Uncommitted Credit Facility
Related Party Transaction [Line Items]
Uncommitted credit facility principle amount		€ 50,000,000
Uncommitted Credit Facility \| LIBOR
Related Party Transaction [Line Items]
Debt basis spread on variable rate		1.00%
Bank of America Merrill Lynch International Ltd. \| Uncommitted Credit Facility
Related Party Transaction [Line Items]
Uncommitted credit facility principle amount	€ 10,000,000						€ 50,000,000
Proceeds from issuance of credit facility		€ 20,000,000	€ 20,000,000
Repayments of debt		40,000,000
Bank of America Merrill Lynch International Ltd. \| Uncommitted Credit Facility \| LIBOR
Related Party Transaction [Line Items]
Debt basis spread on variable rate	1.00%
Principal owner \| Expedia
Related Party Transaction [Line Items]
Revenue from related party		268,200,000	194,200,000	€ 100,200,000
Other operating expenses from related party		4,200,000	2,800,000	1,500,000
Accounts receivable, related party		€ 16,500,000	23,600,000
Related party payable			7,100,000		€ 7,100,000	€ 7,100,000
Proceeds from issuance of loan from related party				1,000,000
Principal owner \| Expedia \| Minimum
Related Party Transaction [Line Items]
Prior notice period on customary commercial terms		3 days
Principal owner \| Expedia \| Maximum
Related Party Transaction [Line Items]
Prior notice period on customary commercial terms		7 days
Principal owner \| Data Hosting Services Agreement \| Expedia
Related Party Transaction [Line Items]
Termination notice period		30 days
Expenses for data hosting services		€ 21,000	€ 21,000	€ 21,000
Principal owner \| Services and Support Agreement \| Expedia
Related Party Transaction [Line Items]
Termination notice period		90 days

Segment information - Schedule of segment information (Details) - EUR (€)
€ in Thousands

1 Months Ended

12 Months Ended

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2014

€ 745,824

€ 490,240

€ 309,152

8,345

2,843

180

754,169

493,083

309,332

623,452

432,173

271,367

Cost of revenue, including related party, excluding amortization

130,717

60,910

37,965

Costs and expenses:

4,273

2,946

1,443

Other selling and marketing

51,277

29,046

14,867

Technology and content

51,658

28,693

15,388

General and administrative, including related party shared service fee

^[1],[2]

54,097

18,065

6,536

Amortization of intangible assets

13,857

30,030

30,025

Operating income (loss)

(44,445)

(47,870)

(30,294)

Other income (expense)

Interest expense

(137)

(147)

(11)

Other, net

(139)

(2,667)

(1,435)

Total other income (expense), net

(276)

(2,814)

(1,446)

Income (loss) before income taxes

(44,721)

(50,684)

(31,740)

Provision for income taxes

6,670

(11,318)

(8,644)

Net loss

€ 1,185

(51,391)

(39,366)

(23,096)

Operating Segments | Developed Europe

348,909

259,568

210,241

348,909

259,568

210,241

257,471

194,886

162,358

Operating Segments | Americas

91,438

64,682

47,883

286,398

171,910

73,316

286,398

171,910

73,316

243,176

169,415

81,110

Operating Segments | Rest of World

43,222

2,495

(7,794)

110,517

58,762

25,595

110,517

58,762

25,595

122,805

67,872

27,899

(12,288)

(9,110)

(2,304)

Corporate & Eliminations

8,345

2,843

180

8,345

2,843

180