Booking (BKNG) 10-Q 7 May 20 2020 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2020	Apr. 30, 2020
Entity Information [Line Items]
Document Type	10-Q
Document Fiscal Period Focus	Q1
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Amendment Flag	false
Document Fiscal Year Focus	2020
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001075531
Entity File Number	1-36691
Entity Registrant Name	Booking Holdings Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	06-1528493
Entity Address, Address Line One	800 Connecticut Avenue
Entity Address, City or Town	Norwalk
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06854
City Area Code	203
Local Phone Number	299-8000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		40,930,911
Common Stock
Entity Information [Line Items]
Title of 12(b) Security	Common Stock par value $0.008 per share
Trading Symbol	BKNG
Security Exchange Name	NASDAQ
0.800% Senior Notes Due 2022
Entity Information [Line Items]
Title of 12(b) Security	0.800% Senior Notes Due 2022
Trading Symbol	BKNG 22A
Security Exchange Name	NASDAQ
2.150% Senior Notes Due 2022
Entity Information [Line Items]
Title of 12(b) Security	2.150% Senior Notes Due 2022
Trading Symbol	BKNG 22
Security Exchange Name	NASDAQ
2.375% Senior Notes Due 2024
Entity Information [Line Items]
Title of 12(b) Security	2.375% Senior Notes Due 2024
Trading Symbol	BKNG 24
Security Exchange Name	NASDAQ
1.800% Senior Notes Due 2027
Entity Information [Line Items]
Title of 12(b) Security	1.800% Senior Notes Due 2027
Trading Symbol	BKNG 27
Security Exchange Name	NASDAQ

UNAUDITED CONSOLIDATED BALANCE

UNAUDITED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 6,363	$ 6,312
Short-term investments (Includes available-for-sale debt securities: Amortized cost of $414 and $998, respectively)	826	998
Accounts receivable, net (Allowance for credit losses of $245 and $49, respectively)	667
Accounts receivable, net (Allowance for credit losses of $245 and $49, respectively)		1,680
Prepaid expenses and other current assets, net (Allowance for credit losses of $5 and $6, respectively)	1,404	843
Total current assets	9,260	9,833
Property and equipment, net	720	738
Operating lease assets	596	620
Intangible assets, net	1,897	1,954
Goodwill	2,391	2,913
Long-term investments (Includes available-for-sale debt securities: Amortized cost of $775 and $2,192, respectively)	2,056	4,477
Other assets, net (Allowance for credit losses of $49 and $0, respectively)	942	867
Total assets	17,862	21,402
Current liabilities:
Accounts payable	926	1,239
Accrued expenses and other current liabilities	1,255	1,578
Deferred merchant bookings	960	1,561
Convertible debt	995	988
Total current liabilities	4,136	5,366
Deferred income taxes	786	876
Operating lease liabilities	438	462
Long-term U.S. transition tax liability	1,021	1,021
Other long-term liabilities	93	104
Long-term debt	7,553	7,640
Total liabilities	14,027	15,469
Commitments and Contingencies
Convertible debt	4	0
Stockholders' equity:
Common stock, $0.008 par value, Authorized shares: 1,000,000,000 Issued shares: 63,369,751 and 63,179,471, respectively	0	0
Treasury stock, 22,439,549 and 21,762,070 shares, respectively	(24,115)	(22,864)
Additional paid-in capital	5,758	5,756
Retained earnings	22,530	23,232
Accumulated other comprehensive loss	(342)	(191)
Total stockholders' equity	3,831	5,933
Total liabilities and stockholders' equity	$ 17,862	$ 21,402

UNAUDITED CONSOLIDATED BALANC_2

UNAUDITED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Accounts receivable, allowance for credit loss	$ 245	$ 49
Prepaid expense, allowance for credit loss	$ 54	$ 6
Common stock, par value (in dollars per share)	$ 0.008	$ 0.008
Common stock, shares authorized (in shares)	1,000,000,000	1,000,000,000
Common stock, shares issued (in shares)	63,369,751	63,179,471
Treasury stock, shares (in shares)	22,439,549	21,762,070
Short-term Investments
Available-for-sale debt securities, amortized cost	$ 414	$ 998
Prepaid Expenses and Other Current Assets
Prepaid expense, allowance for credit loss	5	6
Long-term Investments
Available-for-sale debt securities, amortized cost	775	2,192
Other Assets [Member]
Prepaid expense, allowance for credit loss	$ 49	$ 0

UNAUDITED CONSOLIDATED STATEMEN

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Total revenues	$ 2,288	$ 2,837
Operating expenses:
Marketing expenses	851	1,193
Sales and other expenses	377	215
Personnel, including stock-based compensation of $6 and $74, respectively	484	501
General and administrative	201	191
Information technology	78	65
Depreciation and amortization	117	116
Impairment of goodwill	489	0
Total operating expenses	2,597	2,281
Operating (loss) income	(309)	556
Other income (expense):
Interest income	32	35
Interest expense	(64)	(66)
Net (losses) gains on marketable equity securities	(307)	451
Impairment of investment	(100)	0
Foreign currency transactions and other	26	(8)
Total other (expense) income	(413)	412
(Loss) income before income taxes	(722)	968
Income tax (benefit) expense	(23)	203
Net (loss) income	$ (699)	$ 765
Net income applicable to common stockholders per basic common share (in dollars per share)	$ (17.01)	$ 17.01
Weighted-average number of basic common shares outstanding (in shares)	41,093	45,007
Net income applicable to common stockholders per diluted common share (in dollars per share)	$ (17.01)	$ 16.85
Weighted-average number of diluted common shares outstanding (in shares)	41,093	45,436
Agency revenues
Total revenues	$ 1,424	$ 1,949
Merchant revenues
Total revenues	659	603
Advertising and other revenues
Total revenues	$ 205	$ 285

UNAUDITED CONSOLIDATED STATEM_2

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Stock-based compensation expense	$ 6	$ 74

UNAUDITED CONSOLIDATED STATEM_3

UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Other comprehensive (loss) income, net of tax
Net (loss) income	$ (699)	$ 765
Foreign currency translation adjustments, net of tax	(77)	(12)
Net unrealized (losses) gains on available-for-sale securities, net of tax	(74)	159
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(151)	147
Comprehensive (loss) income	$ (850)	$ 912

UNAUDITED CONSOLIDATED STATEM_4

UNAUDITED CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Balance (in shares) at Dec. 31, 2018		62,949	(17,317)
Balance at Dec. 31, 2018	$ 8,785	$ 0	$ (14,711)	$ 5,445	$ 18,367	$ (316)
Increase (Decrease) in Stockholders' Equity
Net (loss) income	765				765
Foreign currency translation adjustments, net of taxes	(12)					(12)
Net unrealized gains (losses) on debt securities, net of taxes	159					159
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)		173
Exercise of stock options and vesting of restricted stock units and performance share units	$ 0	$ 0		0
Repurchase of common stock (in shares)	(1,619)		(1,619)
Repurchase of common stock	$ (2,856)		$ (2,856)
Stock-based compensation and other stock-based payments	74			74
Balance (in shares) at Mar. 31, 2019		63,122	(18,936)
Balance at Mar. 31, 2019	6,915	$ 0	$ (17,567)	5,519	19,132	(169)
Balance (in shares) at Dec. 31, 2019		63,179	(21,762)
Balance at Dec. 31, 2019	5,933	$ 0	$ (22,864)	5,756	23,232	(191)
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(699)				(699)
Foreign currency translation adjustments, net of taxes	(77)					(77)
Net unrealized gains (losses) on debt securities, net of taxes	(74)					(74)
Reclassification adjustment for convertible debt in mezzanine	(4)			(4)
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)		191
Exercise of stock options and vesting of restricted stock units and performance share units	$ 0	$ 0		0
Repurchase of common stock (in shares)	(678)		(678)
Repurchase of common stock	$ (1,251)		$ (1,251)
Stock-based compensation and other stock-based payments	6			6
Balance (in shares) at Mar. 31, 2020		63,370	(22,440)
Balance at Mar. 31, 2020	$ 3,831	$ 0	$ (24,115)	$ 5,758	$ 22,530	$ (342)

UNAUDITED CONSOLIDATED STATEM_5

UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Cash Flows [Abstract]
Net (loss) income	$ (699)	$ 765
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Depreciation and amortization	117	116
Provision for expected credit losses and chargebacks	262	40
Deferred income tax (benefit) expense	(97)	89
Net losses (gains) on marketable equity securities	307	(451)
Stock-based compensation expense and other stock-based payments	11	78
Operating lease amortization	46	42
Amortization of debt discount and debt issuance costs	14	14
Unrealized foreign currency transaction gains on Euro-denominated debt	(33)	0
Impairment of goodwill	489	0
Impairment of investment	100	0
Other	2	7
Changes in assets and liabilities:
Accounts receivable	760	(24)
Prepaid expenses and other current assets	(445)	(669)
Deferred merchant bookings and other current liabilities	(1,135)	561
Other long-term assets and liabilities	(79)	(418)
Net cash (used in) provided by operating activities	(380)	150
INVESTING ACTIVITIES:
Purchase of investments	(72)	(445)
Proceeds from sale and maturity of investments	1,885	2,665
Additions to property and equipment	(80)	(111)
Net cash provided by investing activities	1,733	2,109
FINANCING ACTIVITIES:
Proceeds from revolving credit facility and short-term borrowings	0	250
Repayments of short-term borrowings	0	(25)
Payments for repurchase of common stock	(1,281)	(2,773)
Net cash used in financing activities	(1,281)	(2,548)
Effect of exchange rate changes on cash and cash equivalents and restricted cash and cash equivalents	(21)	(2)
Net increase (decrease) in cash and cash equivalents and restricted cash and cash equivalents	51	(291)
Total cash and cash equivalents and restricted cash and cash equivalents, beginning of period (see Note 14)	6,332	2,645
Total cash and cash equivalents and restricted cash and cash equivalents, end of period (see Note 14)	6,383	2,354
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid during the period for income taxes (see Note 14)	762	816
Cash paid during the period for interest	$ 68	$ 68

BASIS OF PRESENTATION

BASIS OF PRESENTATION	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATION Management of Booking Holdings Inc. (the "Company") is responsible for the Unaudited Consolidated Financial Statements included in this document. The Unaudited Consolidated Financial Statements have been prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") and include all normal and recurring adjustments that management of the Company considers necessary for a fair presentation of its financial position and operating results. The Company prepared the Unaudited Consolidated Financial Statements following the requirements of the Securities and Exchange Commission for interim reporting. As permitted under those rules, the Company condensed or omitted certain footnotes or other financial information that are normally required by GAAP for annual financial statements. These statements should be read in combination with the Consolidated Financial Statements in the Company's Annual Report on Form 10-K for the year ended December 31, 2019 . The Unaudited Consolidated Financial Statements include the accounts of the Company and its wholly-owned subsidiaries. All inter-company accounts and transactions have been eliminated in consolidation. The functional currency of the Company's subsidiaries is generally the respective local currency. For international operations, assets and liabilities are translated into U.S. Dollars at the rate of exchange existing at the balance sheet date. Income statement amounts are translated at monthly average exchange rates applicable for the period. Translation gains and losses are included as a component of " Accumulated other comprehensive loss " in the accompanying Consolidated Balance Sheets. Foreign currency transaction gains and losses are included in "Foreign currency transactions and other" in the Unaudited Consolidated Statements of Operations. Revenues, expenses, assets and liabilities can vary during each quarter of the year. Therefore, the results and trends in these interim financial statements may not be the same as those for any subsequent quarter or the full year, especially during the periods that are impacted by the COVID-19 pandemic. Impact of COVID-19 In December 2019, a novel strain of coronavirus, COVID-19, was first detected in Wuhan, China, and has since spread to other regions, including Europe and the United States. On March 11, 2020, the World Health Organization declared that the rapidly spreading COVID-19 outbreak was a global pandemic (the "COVID-19 pandemic"). In response to the COVID-19 pandemic, many governments around the world have implemented, and continue to implement, a variety of measures to reduce the spread of COVID-19, including travel restrictions and bans, instructions to residents to practice social distancing, quarantine advisories, shelter-in-place orders and required closures of non-essential businesses. These government mandates have forced many of the customers on whom the Company’s business relies, including hotels and other accommodation providers, airlines and restaurants, to seek government support in order to continue operating, to curtail drastically their service offerings or to cease operations entirely. Further, these measures have materially adversely affected, and may further adversely affect, consumer sentiment and discretionary spending patterns, economies and financial markets, and the Company’s workforce, operations and customers. The COVID-19 pandemic and the resulting economic conditions and government orders have resulted in a material decrease in consumer spending and an unprecedented decline in travel and restaurant activities and consumer demand for related services. The Company’s financial results and prospects are almost entirely dependent on the sale of such travel and restaurant-related services. The Company’s results for the quarter ended March 31, 2020 have been significantly and negatively impacted as compared to the corresponding period in 2019. Due to the uncertain and rapidly evolving nature of current conditions around the world, the Company is unable to predict accurately the impact that the COVID-19 pandemic will have on its business going forward. The Company currently expects, however, that the COVID-19 pandemic will impact its financial performance for the quarter ended June 30, 2020, much more significantly than it impacted the quarter ended March 31, 2020, primarily because an increasing number of markets and locations will have been subject to the governmental measures and economic disruptions noted above during the entirety of the second quarter (as compared to the first quarter, when the effects of the outbreak were largely limited to China and certain other Asian markets during January 2020 and much of February 2020). With the spread of COVID-19 to other regions, such as Europe and the United States, the Company expects the COVID-19 pandemic and its effects to continue to have a significant adverse impact on its business for the duration of the pandemic and during the subsequent economic recovery, which could be an extended period of time. Given the volatility in global markets and the financial difficulties faced by many of the Company's travel service provider and restaurant customers and marketing affiliates, the Company has increased its provision for expected credit losses (also referred to as provision for bad debt or provision for uncollectible accounts) on receivables from and prepayments to its travel service provider and restaurant customers and marketing affiliates (see Note 7 ). Moreover, due to the high level of cancellations of existing reservations, the Company has incurred, and expects to continue to incur, higher than normal cash outlays to refund consumers for prepaid reservations (see Note 2 ). Any material increase in the Company’s provision for expected credit losses and any material increase in cash outlays to consumers would have a corresponding adverse effect on the Company's results of operations and related cash flows. As a result of the deterioration of the Company’s business due to the COVID-19 pandemic, the Company has determined that a portion of its goodwill has experienced a decline in value at March 31, 2020 and recorded a significant impairment charge (see Note 8 ). In addition, the Company has recorded a significant impairment charge for one of the Company's long-term investments due to the impact of the COVID-19 pandemic on the business of the investee and the Company's estimate of the resulting decline in the value of the investment (see Notes 5 and 6 ). It is possible that the Company may also have to record additional significant impairment charges in future periods. See Note 9 for additional information about the Company’s existing debt arrangements, including $4.1 billion of debt issued in April 2020. The Company’s continued access to sources of liquidity depends on multiple factors, including global economic conditions, the condition of global financial markets, the availability of sufficient amounts of financing, the Company’s operating performance and its credit ratings. If the Company’s credit ratings were to be downgraded, or financing sources were to ascribe higher risk to its rating levels, the Company or its industry, the Company’s access to capital and the cost of any financing would be negatively impacted. There is no guarantee that additional debt financing will be available in the future to fund the Company’s obligations, or that it will be available on commercially reasonable terms, in which case the Company may need to seek other sources of funding. The extent of the effects of the COVID-19 pandemic on the Company’s business, results of operations, cash flows and growth prospects is highly uncertain and will ultimately depend on future developments. These include, but are not limited to, the severity, extent and duration of the pandemic and its impact on the travel and restaurant industries and consumer spending more broadly. Even if economic and operating conditions for the Company’s business improve, the Company cannot predict the long-term effects of the pandemic on its business or the travel and restaurant industries as a whole. If the travel and restaurant industries are fundamentally changed by the COVID-19 pandemic in ways that are detrimental to the Company’s operating model, the Company’s business may continue to be adversely affected even as the broader global economy recovers. Certain governments have passed or are considering legislation to help businesses weather the COVID-19 pandemic through loans, wage subsidies, tax relief or other financial aid. Subsequent to March 31, 2020. the Company is participating in, or has applied to participate in, the United Kingdom's job retention scheme, the Netherlands' wage subsidy program and certain other jurisdictions' programs, and is assessing whether it will take advantage of any other offerings. Change in Presentation and Reclassification In the year ended December 31, 2019 and prior periods, the Company's marketing expenses were presented in the Consolidated Statements of Operations as "Performance marketing" and "Brand marketing" expenses. In the first quarter of 2020, the Company changed the presentation of marketing expenses by combining "Performance marketing" and "Brand marketing" into "Marketing expenses" in the Unaudited Consolidated Statement of Operations because of the increased convergence of performance marketing and brand marketing channels in areas including digital marketing and the Company's view of overall marketing expenditure as its investment in customer acquisition and retention. The change in presentation had no impact on operating income or net income. The Unaudited Statement of Operations for the three months ended March 31, 2019 has been recast to conform to the current year presentation. In addition to the change in presentation for marketing expenses, certain amounts from prior periods have been reclassified to conform to the current period presentation. Recent Accounting Pronouncements Adopted Simplifying the Test for Goodwill Impairment In January 2017, the Financial Accounting Standards Board ("FASB") issued a new accounting update to simplify the test for goodwill impairment. The revised guidance eliminates the previously required step two of the goodwill impairment test, which required a hypothetical purchase price allocation to measure goodwill impairment. Under the revised guidance, a goodwill impairment loss will be measured at the amount by which a reporting unit’s carrying amount exceeds its fair value, not to exceed the carrying amount of goodwill. The Company adopted this update in the first quarter of 2020 and applied it on a prospective basis (see Note 8 for further information on the goodwill impairment test performed at March 31, 2020). Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued a new accounting update on the measurement of credit losses for certain financial assets measured at amortized cost and available-for-sale debt securities. For financial assets measured at amortized cost, this update requires an entity to (1) estimate its lifetime expected credit losses upon recognition of the financial assets and establish an allowance to present the net amount expected to be collected, (2) recognize this allowance and changes in the allowance during subsequent periods through net income and (3) consider relevant information about past events, current conditions and reasonable and supportable forecasts in assessing the lifetime expected credit losses. For available-for-sale debt securities, this update made several targeted amendments to the existing other-than-temporary impairment model, including (1) requiring disclosure of the allowance for credit losses, (2) allowing reversals of the previously recognized credit losses until the entity has the intent to sell, is more-likely-than-not required to sell the securities or the maturity of the securities, (3) limiting impairment to the difference between the amortized cost basis and fair value and (4) not allowing entities to consider the length of time that fair value has been less than amortized cost as a factor in evaluating whether a credit loss exists. The Company adopted this update in the first quarter of 2020 and applied this update on a modified retrospective basis. Upon adoption of the new standard on January 1, 2020, the Company recorded a net decrease to its retained earnings of $3 million , net of tax. See Note 7 for further information related to allowance for expected credit losses on accounts receivable and other financial assets and Note 5 for further information related to investments in available-for-sale debt securities. Other Recent Accounting Pronouncement Simplifying the Accounting for Income Taxes In December 2019, the FASB issued a new accounting update relating to income taxes. This update provides an exception to the general methodology for calculating income taxes in an interim period when a year-to-date loss exceeds the anticipated loss for the year. This update also (1) requires an entity to recognize a franchise tax (or similar tax) that is partially based on income as an income-based tax and account for any incremental amount incurred as a non-income-based tax, (2) requires an entity to evaluate when a step-up in the tax basis of goodwill should be considered part of the business combination in which goodwill was originally recognized for accounting purposes and when it should be considered a separate transaction, and (3) requires that an entity reflect the effect of an enacted change in tax laws or rates in the annual effective tax rate computation in the interim period that includes the enactment date.

REVENUE

REVENUE	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
REVENUE RECOGNITION	REVENUE Disaggregation of revenue Geographic Information The Company's international information consists of the results of Booking.com, agoda and Rentalcars.com in their entirety and the results of the international businesses of KAYAK and OpenTable. This classification is independent of where the consumer resides, where the consumer is physically located while using the Company's services or the location of the travel service provider or restaurant. For example, a reservation made through Booking.com (which is domiciled in the Netherlands) at a hotel in New York by a consumer in the United States is part of the Company's international results. The Company's geographic information is as follows (in millions): International United States The Netherlands Other Total Total revenues for the three months ended March 31, 2020 $ 285 $ 1,677 $ 326 $ 2,288 2019 (1) 366 2,072 399 2,837 (1) Geographic information for the three months ended March 31, 2019 has been recast to conform to the current period presentation. Revenue by Type of Service Approximately 85% and 84% of the Company's revenue for the three months ended March 31, 2020 and 2019 , respectively, relates to online accommodation reservation services. Revenue from all other sources of online travel reservation services and advertising and other revenues each represent less than 10% of the Company's total revenues. Deferred Revenue Cash payments received from travelers in advance of the Company completing its service obligations are included in "Deferred merchant bookings" in the Company's Consolidated Balance Sheets and are comprised principally of amounts estimated to be payable to the travel service providers as well as the Company's estimated deferred revenue for its commission or margin and fees. The Company expects to complete its service obligation within one year from the reservation date. The amounts are subject to refunds for cancellations. The following table summarizes the activity of deferred revenue for online travel reservation services for the three months ended March 31, 2020 (in millions): Balance, December 31, 2019 $ 220 Revenues recognized from the beginning deferred revenue balance (150 ) Cancellations (46 ) Payments received from travelers, net of amounts estimated to be payable to travel service providers, and other 120 Balance, March 31, 2020 $ 144 Loyalty and Other Incentive Programs The Company provides loyalty programs where participating consumers are awarded loyalty points on current transactions that can be redeemed in the future. At March 31, 2020 and December 31, 2019 , liabilities for loyalty program incentives of $76 million and $80 million , respectively, were included in "Accrued expenses and other current liabilities" in the Consolidated Balance Sheets. The Company’s largest loyalty program is at OpenTable, where points can be redeemed for rewards such as qualifying reservations at participating restaurants, third-party gift cards and accommodation reservations booked through some of the Company’s other platform s. The estimated fair value of the loyalty points that are expected to be redeemed is recognized as a reduction of revenue at the time the incentives are granted. In addition to the loyalty programs, at March 31, 2020 and December 31, 2019 , liabilities of $22 million for other incentive programs, such as referral bonuses, credits and discounts, were included in "Accrued expenses and other current liabilities" in the Consolidated Balance Sheets. Impact of COVID-19 Due to the high level of cancellations of existing reservations as a result of the COVID-19 pandemic (see Note 1 ), the Company has incurred, and expects to continue to incur, higher than normal cash outlays to refund travelers for prepaid reservations, including certain situations where the Company has already transferred the prepayment to the travel service provider. For the three months ended March 31, 2020, the Company recorded a reduction in revenue of $63 million for refunds paid or estimated to be payable to travelers where the Company has agreed to provide free cancellation for certain non-refundable reservations without a corresponding estimated expected recovery from the travel service providers.

STOCK-BASED EMPLOYEE COMPENSATI

STOCK-BASED EMPLOYEE COMPENSATION	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
STOCK-BASED EMPLOYEE COMPENSATION	STOCK-BASED EMPLOYEE COMPENSATION Stock-based compensation expense included in "Personnel" expenses in the Unaudited Consolidated Statements of Operations was $6 million and $74 million for the three months ended March 31, 2020 and 2019 , respectively. Stock-based compensation expense related to performance share units, restricted stock units and stock options is recognized based on fair value on a straight-line basis over the respective requisite service periods and forfeitures are accounted for when they occur. The fair value on the grant date of performance share units and restricted stock units is determined based on the number of units granted and the quoted price of the Company's common stock. The fair value of employee stock options assumed in acquisitions was determined using the Black-Scholes model and the market value of the Company's common stock at the respective acquisition dates. The Company records stock-based compensation expense for performance-based awards using its estimate of the probable outcome at the end of the performance period (i.e., the estimated performance against the performance targets). The Company periodically adjusts the cumulative stock-based compensation expense recorded when the probable outcome for these performance-based awards is updated based upon changes in actual and forecasted operating results. For the performance share units outstanding at March 31, 2020, due to the impact of the COVID-19 pandemic (see Note 1), there is a significant decline in the estimated performance over the performance periods against the performance targets. At March 31, 2020, there was a significant reduction in the number of shares that were probable to be issued as compared to December 31, 2019. As a result, in the three months ended March 31, 2020, the Company recognized a reduction in stock-based compensation expense of $73 million , which is included in "Personnel" expense in the Unaudited Consolidated Statement of Operations. Restricted stock units granted by the Company during the three months ended March 31, 2020 had aggregate grant-date fair values of $265 million . Restricted stock units and performance share units that vested during the three months ended March 31, 2020 had aggregate fair values at vesting of $319 million . At March 31, 2020 , there was $541 million of estimated total future stock-based compensation expense related to unvested share-based awards to be recognized over a weighted-average period of 2.3 years . Restricted Stock Units The Company makes broad-based grants of restricted stock units that generally vest during a period of one - to three -years, subject to certain exceptions for terminations other than for "cause," for "good reason" or on account of death or disability. The following table summarizes the activity of restricted stock units for employees and non-employee directors during the three months ended March 31, 2020 : Restricted Stock Units Shares Weighted-average Grant-date Fair Value Per Share Unvested at December 31, 2019 256,745 $ 1,801 Granted 152,832 $ 1,732 Vested (109,595 ) $ 1,808 Forfeited (5,971 ) $ 1,805 Unvested at March 31, 2020 294,011 $ 1,762 Performance Share Units The Company grants performance share units to executives and certain other employees, which generally vest at the end of a three -year period, subject to certain exceptions for terminations other than for "cause," for "good reason" or on account of death or disability. Performance share units are payable in shares of the Company's common stock upon vesting. The number of shares which ultimately will vest depends on achieving certain performance metrics by the end of the performance period, assuming there is no accelerated vesting for, among other things, a termination of employment under certain circumstances. The following table summarizes the activity of performance share units for employees during the three months ended March 31, 2020 : Performance Share Units Shares Weighted-average Grant-date Fair Value Per Share Unvested at December 31, 2019 216,083 $ 1,835 Vested (80,266 ) $ 1,737 Performance Shares Adjustment * (58,427 ) $ 1,957 Forfeited (2,989 ) $ 1,834 Unvested at March 31, 2020 74,401 $ 1,841 * Probable outcome for these performance-based awards is updated based upon changes in actual and forecasted operating results. No performance share units were granted during the three months ended March 31, 2020. The following table summarizes the estimated vesting, as of March 31, 2020 , of performance share units granted in 2019 and 2018 , net of forfeiture and vesting since the respective grant dates: Performance Share Units, by grant year 2019 2018 Shares probable to be issued 45,361 29,040 Shares not subject to the achievement of minimum performance thresholds 45,361 28,647 Shares that could be issued if maximum performance thresholds are met 117,558 79,914 Stock Options All outstanding employee stock options were assumed in acquisitions, and generally have a term of 10 years from the grant date. The following table summarizes the activity for stock options during the three months ended March 31, 2020 : Employee Stock Options Number of Shares Weighted-average Aggregate Intrinsic Value (in millions) Weighted-average Remaining Contractual Term Balance, December 31, 2019 15,122 $ 484 $ 24 2.6 Exercised (100 ) $ 334 Balance, March 31, 2020 15,022 $ 485 $ 13 2.4 Vested and exercisable at March 31, 2020 15,022 $ 485 $ 13 2.4

NET INCOME PER SHARE

NET INCOME PER SHARE	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
NET INCOME PER SHARE	NET (LOSS) INCOME PER SHARE The Company computes basic net (loss) income per share by dividing net (loss) income applicable to common stockholders by the weighted-average number of common shares outstanding during the period. Diluted net income per share is based upon the weighted-average number of common and common equivalent shares outstanding during the period. Common equivalent shares related to stock options, restricted stock units and performance share units are calculated using the treasury stock method. Performance share units are included in the weighted-average common equivalent shares based on the number of shares that would be issued if the end of the reporting period were the end of the performance period, if the result would be dilutive. The Company's convertible notes have net share settlement features requiring the Company upon conversion to settle the principal amount of the debt for cash and the conversion premium for cash or shares of the Company's common stock, at the Company's option. Under the treasury stock method, if the conversion prices for the convertible notes exceed the Company's average stock price for the period, the convertible notes generally have no impact on diluted net income per share. The convertible notes are included in the calculation of diluted net income per share if their inclusion is dilutive under the treasury stock method. A reconciliation of the weighted-average number of shares outstanding used in calculating diluted net (loss) income per share is as follows (in thousands): Three Months Ended 2020 2019 Weighted-average number of basic common shares outstanding 41,093 45,007 Weighted-average dilutive stock options, restricted stock units and performance share units — 229 Assumed conversion of convertible senior notes — 200 Weighted-average number of diluted common and common equivalent shares outstanding 41,093 45,436 For the three months ended March 31, 2020, 259,000 potential common shares principally related to restricted stock units, performance share units and convertible senior notes were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the period.

INVESTMENTS

INVESTMENTS	3 Months Ended
	Mar. 31, 2020
Investments, Debt and Equity Securities [Abstract]
INVESTMENTS	INVESTMENTS The following table summarizes, by major security type, the Company's investments at March 31, 2020 (in millions): Cost Gross Unrealized Gains Gross Unrealized Losses Carrying Value Short-term investments: Debt securities: Corporate debt securities $ 164 $ — $ — $ 164 Trip.com Group convertible debt securities 250 — (2 ) 248 Equity securities: Trip.com Group equity securities 531 — (117 ) 414 Total $ 945 $ — $ (119 ) $ 826 Long-term investments: Investments in private companies: Debt securities $ 250 $ — $ (20 ) $ 230 Equity securities 501 — (100 ) 401 Other long-term investments: Debt securities: Trip.com Group convertible debt securities 525 — (77 ) 448 Equity securities 461 522 (6 ) 977 Total $ 1,737 $ 522 $ (203 ) $ 2,056 The following table summarizes, by major security type, the Company's investments at December 31, 2019 (in millions): Cost Gross Unrealized Gains Gross Unrealized Losses Carrying Value Short-term investments: Debt securities: International government securities $ 109 $ — $ — $ 109 U.S. government securities 138 — — 138 Corporate debt securities 751 1 (1 ) 751 Total $ 998 $ 1 $ (1 ) $ 998 Long-term investments: Investments in private companies: Debt securities $ 250 $ — $ — $ 250 Equity securities 501 — — 501 Other long-term investments: Debt securities: International government securities 68 — — 68 U.S. government securities 136 — (1 ) 135 Corporate debt securities 963 2 (2 ) 963 Trip.com Group convertible debt securities 775 — (8 ) 767 Equity securities 1,117 684 (8 ) 1,793 Total $ 3,810 $ 686 $ (19 ) $ 4,477 The Company assesses the classification of its investments in the Consolidated Balance Sheets as short-term or long-term at the individual security level. Classification as short-term or long-term is based upon the maturities of the securities, as applicable, and the Company's expectations regarding the timing of sales and redemptions. Investments of a strategic nature that have been made for the purpose of affiliation or potential business advantage or in connection with a commercial relationship are included in "Long-term investments" in the Consolidated Balance Sheets, except in situations where the Company expects the investment to be realized in cash, redeemed or sold within one year. At March 31, 2020, the Company reclassified $103 million of investments in debt securities with maturities greater than one year to short-term investments as the Company expects to sell the securities within one year. At December 31, 2019, these investments were classified as long-term investments. In addition, at March 31, 2020, $250 million of Trip.com Group convertible notes due May 2020 are classified as a short-term investment. At December 31, 2019, the investment was classified as a long-term investment based on the Company’s expectations at that time regarding the strategic investment. At March 31, 2020, investments in Trip.com Group American Depositary Shares ("ADSs") with a fair value of $414 million were reclassified to short-term investments as the Company expects to sell the securities within one year. At December 31, 2019, such investments were classified as long-term investments. The Company has classified its investments in debt securities as available-for-sale securities. Preferred stock that is either mandatorily redeemable or redeemable at the option of the investor is also considered a debt security for accounting purposes. Available-for-sale debt securities are reported at estimated fair value (see Note 6 ) with the aggregate unrealized gains and losses, net of tax, reflected in "Accumulated other comprehensive loss" in the Consolidated Balance Sheets. If the amortized cost basis of an available-for-sale security exceeds its fair value and if the Company has the intention to sell the security or it is more likely than not that the Company will be required to sell the security before recovery of the amortized cost basis, an impairment is recognized in the Unaudited Consolidated Statements of Operations. If the Company does not have the intention to sell the security and it is not more likely than not that the Company will be required to sell the security before recovery of the amortized cost basis and the Company determines that the decline in fair value below the amortized cost basis of an available-for-sale security is entirely or partially due to credit-related factors, the credit loss is measured and recognized as an allowance for credit losses along with the related expense in the Unaudited Consolidated Statements of Operations. The allowance is measured as the amount by which the debt security’s amortized cost basis exceeds the Company’s best estimate of the present value of cash flows expected to be collected. The fair values of these investments are based on the specific quoted market price of the securities or comparable securities at the balance sheet dates. Unobservable inputs are also used when little or no market data is available. See Note 6 for information related to fair value measurements. Investments in equity securities include marketable equity securities and equity investments without readily determinable fair values. Marketable equity securities are reported at estimated fair value with changes in fair value recognized in "Net gains (losses) on marketable equity securities" in the Unaudited Consolidated Statements of Operations. The Company also holds investments in equity securities of private companies, over which the Company does not have the ability to exercise significant influence or control. The Company has elected to measure these investments at cost less impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. Investments in Government and Corporate Debt Securities The Company has classified its investments in international government securities, U.S. government securities and corporate debt securities as available-for-sale securities. The Company's investment policy seeks to preserve capital and maintain sufficient liquidity to meet operational and other needs of the business. At March 31, 2020 , the weighted-average life of the Company’s investments in these debt securities, was approximately 0.8 years with an average credit quality of A+/A2/A. At March 31, 2020, the Company recorded an impairment of $3 million for investments in certain corporate debt securities as their respective fair values were lower than their amortized cost basis and the Company had the intention to sell the securities. The difference between the fair value and the amortized cost basis of each of these securities was recorded in " Foreign currency transactions and other " in the Unaudited Consolidated Statement of Operations for the three months ended March 31, 2020. In addition, subsequent to March 31, 2020, the Company realized $164 million in cash from the sales and maturities of its remaining investments in corporate debt securities. Investments in Trip.com Group At March 31, 2020 , the Company had $775 million invested in convertible senior notes issued at par value by Trip.com Group with maturity dates ranging from May 2020 to December 2025. The strategic investments in Trip.com Group convertible senior notes, excluding $250 million of convertible notes due May 2020, were classified as "Long-term investments" in the Consolidated Balance Sheet at March 31, 2020 . At March 31, 2020, the fair values of the Company’s investments in the convertible notes were lower than their respective amortized cost basis. At March 31, 2020 , the Company did not have the intent or a requirement to sell its investment in Trip.com Group convertible debt securities prior to their anticipated recovery. The Company believes that the decline in fair values of the investments are largely due to changes in market and economic conditions related to the COVID-19 pandemic (see Note 1 ), which had a negative impact on Trip.com's share price and other market conditions. The Company reviewed available information to evaluate Trip.com's financial solvency and at March 31, 2020 expects recovery of the amortized cost basis of the investments. At December 31, 2019 , the Company had $655 million invested in Trip.com Group ADSs with a fair value of $726 million , which is reported in "Long-term investments" in the Consolidated Balance Sheet. In the three months ended March 31, 2020 , the Company sold a portion of its investment in the ADSs, with a cost basis of $124 million , for $94 million . " Net (losses) gains on marketable equity securities " in the Unaudited Consolidated Statement of Operations for the three months ended March 31, 2020 includes a loss of $40 million related to the ADSs sold during the period and an unrealized loss of $178 million related to the ADSs held by the Company at March 31, 2020 . " Net (losses) gains on marketable equity securities " in the Unaudited Consolidated Statement of Operations for the three months ended March 31, 2019 includes a net unrealized gain of $360 million related to the ADSs. Certain Trip.com Group convertible notes include a put option allowing the Company, at certain points of time, to require, at its option, redemption of the convertible notes and repayment in cash from Trip.com Group. The Company determined that the economic characteristics and risks of the put options are clearly and closely related to the notes, and therefore did not meet the requirement for separate accounting as embedded derivatives. The Company monitors the conversion features of these notes to determine whether they meet the definition of an embedded derivative during each reporting period. The conversion feature associated with the $25 million convertible notes issued in 2016 meets the definition of an embedded derivative that requires separate accounting. The embedded derivative is bifurcated for fair value measurement purposes only and is reported in the Consolidated Balance Sheets with its host contract in "Long-term investments." The mark-to-market adjustments of the embedded derivative are included in "Foreign currency transactions and other" in the Company's Unaudited Consolidated Statements of Operations. Subsequent to March 31, 2020, the Company sold its remaining investment in the ADSs, with a cost basis of $531 million , for $431 million . Investment in Meituan Dianping In 2017, the Company invested $450 million in preferred shares of Meituan Dianping, the leading e-commerce platform for local services in China. The investment has been converted to ordinary shares and classified as a marketable equity security since Meituan Dianping's initial public offering in 2018. The investment had fair values of $972 million and $1.1 billion at March 31, 2020 and December 31, 2019 , respectively, which is included in "Long-term investments" in the Consolidated Balance Sheets. For the three months ended March 31, 2020 and 2019, respectively, net unrealized loss of $81 million and a net unrealized gain of $91 million , related to this investment, are included in " Net (losses) gains on marketable equity securities " in the Unaudited Consolidated Statements of Operations. Investments in Private Companies Equity Securities without Readily Determinable Fair Values The Company had $501 million invested in equity securities of private companies at March 31, 2020 and December 31, 2019 , including $500 million invested in Didi Chuxing. These investments are measured at cost less impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer and are included in "Long-term investments" in the Company's Consolidated Balance Sheets. Considering the impact of the COVID-19 pandemic (see Note 1), the Company performed an impairment analysis on the investment in Didi Chuxing at March 31, 2020 and recognized an impairment charge of $100 million , resulting in an adjusted carrying value of $400 million at March 31, 2020 (see Note 6). Debt Securities The Company had $250 million invested in preferred shares of private companies, including Grab Holdings Inc. ("Grab"), with an aggregate fair value of $230 million and $250 million at March 31, 2020 and December 31, 2019 , respectively. These investments are classified as debt securities for accounting purposes and categorized as available-for-sale. The preferred shares are convertible to ordinary shares at the Company’s option and are mandatorily convertible upon an initial public offering. The preferred shares also contain a redemption feature that can be exercised by the Company after certain points of time. These features have been evaluated as embedded derivatives, however, they do not meet the requirements to be accounted for separately. The fair value of the Company's investment in Grab was $180 million and $200 million at March 31, 2020 and December 31, 2019, respectively (see Note 6). The Company recognized an unrealized loss of $20 million related to the investment in Grab in "Accumulated other comprehensive loss" in the Consolidated Balance Sheets at March 31, 2020. At March 31, 2020, the Company did not have the intent or a requirement to sell its investment in Grab. The Company believes that the decline in fair value of the investment is largely due to changes in market and economic conditions related to the COVID-19 pandemic (see Note 1). The Company also reviewed other available information and at March 31, 2020, expects recovery of the amortized cost basis of the investment.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS Financial assets and liabilities carried at fair value at March 31, 2020 are classified in the categories described in the table below (in millions): Level 1 Level 2 Level 3 Total Recurring fair value measurements ASSETS: Cash equivalents and restricted cash equivalents: Money market funds $ 5,944 $ — $ — $ 5,944 Time deposits and certificates of deposit 26 — — 26 Short-term investments: Corporate debt securities — 164 — 164 Trip.com Group convertible debt securities — 248 — 248 Trip.com Group equity securities 414 — — 414 Long-term investments: Investments in private companies: Debt securities — — 230 230 Other long-term investments: Trip.com Group convertible debt securities — 448 — 448 Equity securities 977 — — 977 Derivatives: Foreign currency exchange derivatives — 12 — 12 Total assets at fair value $ 7,361 $ 872 $ 230 $ 8,463 LIABILITIES: Foreign currency exchange derivatives $ — $ 21 $ — $ 21 Nonrecurring fair value measurements Investment in Didi Chuxing $ — $ — $ 400 $ 400 Goodwill of the OpenTable and KAYAK reporting unit — — 1,545 1,545 Total nonrecurring fair value measurements $ — $ — $ 1,945 $ 1,945 Financial assets and liabilities carried at fair value at December 31, 2019 are classified in the categories described in the table below (in millions): Level 1 Level 2 Level 3 Total Recurring fair value measurements ASSETS: Cash and restricted cash equivalents: Money market funds $ 5,734 $ — $ — $ 5,734 Corporate debt securities — 2 — 2 Time deposits and certificates of deposit 29 — — 29 Short-term investments: International government securities — 109 — 109 U.S. government securities — 138 — 138 Corporate debt securities — 751 — 751 Long-term investments: Investments in private companies: Debt securities — — 250 250 Other long-term investments: International government securities — 68 — 68 U.S. government securities — 135 — 135 Corporate debt securities — 963 — 963 Trip.com Group convertible debt securities — 767 — 767 Equity securities 1,793 — — 1,793 Derivatives: Foreign currency exchange derivatives — 12 — 12 Total assets at fair value $ 7,556 $ 2,945 $ 250 $ 10,751 LIABILITIES: Foreign currency exchange derivatives $ — $ 5 $ — $ 5 There are three levels of inputs to measure fair value. The definition of each input is described below: Level 1 : Quoted prices in active markets that are accessible by the Company at the measurement date for identical assets and liabilities. Level 2 : Inputs that are observable, either directly or indirectly. Such prices may be based upon quoted prices for identical or comparable securities in active markets or inputs not quoted on active markets, but corroborated by market data. Level 3 : Unobservable inputs are used when little or no market data is available. Rollforward of Level 3 Fair Value Measurements Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Debt securities (in millions) Balance, December 31, 2019 $ 250 Total losses for the period: Total unrealized losses included in accumulated other comprehensive loss (1) (20 ) Balance, March 31, 2020 $ 230 (1) These losses are recorded in “Accumulated other comprehensive loss” in the Consolidated Balance Sheet. Investments See Note 5 for further information related to the Company's investments. The valuation of investments in corporate debt securities, U.S. and international government securities and Trip.com Group convertible debt securities are considered "Level 2 " valuations because the Company has access to quoted prices, but does not have visibility into the volume and frequency of trading for these investments. A market approach is used for recurring fair value measurements and the valuation techniques use inputs that are observable, or can be corroborated by observable data, in an active marketplace. Investments in private companies measured using Level 3 inputs The Company’s investments measured using Level 3 inputs primarily consist of preferred stock investments in privately-held companies that are classified as either debt securities or equity securities without readily determinable fair values. Fair values of privately held securities are estimated using a variety of valuation methodologies, including both market and income approaches. The Company has used valuation techniques appropriate for the type of investment and the information available about the investee as of the valuation date to determine fair value. Recent financing transactions in the investee, such as new investments in preferred stock, are generally considered the best indication of the enterprise value and therefore used as a basis to estimate fair value. However, based on a number of factors, such as the proximity in timing to the valuation date or the volume or other terms of these financing transactions, the Company may also use other valuation techniques to supplement this data, including the income approach. In addition, an option-pricing model (“OPM”) is utilized to allocate value to the various classes of securities of the investee, including the class owned by the Company. The model includes assumptions around the investees’ expected time to liquidity and volatility. At March 31, 2020, the fair values of the Company's investments in Didi and Grab, measured using Level 3 inputs, were $400 million and $180 million , respectively. As discussed below, the Company used unobservable inputs in order to determine fair value. The Company used an income approach in estimating the fair value of Didi and a relative weighting of 75% income approach and 25% recent financing transactions in estimating the fair value of Grab. The income approach estimates value based on the expectation of future cash flows that a company will generate. These future cash flows are discounted to their present values using a discount rate based on a company’s weighted-average cost of capital, and is adjusted to reflect the risks inherent in its cash flows. The key unobservable inputs and ranges used for these investments include the weighted average cost of capital ( 12% - 14% ), terminal Earnings before income taxes, depreciation and amortization (“EBITDA”) Multiple ( 13 x- 15 x), volatility ( 60% - 70% ) and an estimated time to liquidity of 4 years. Significant changes in any of these inputs in isolation would result in significantly different fair value measurements. Generally, a change in the assumption used for terminal EBITDA multiples would result in a directionally similar change in the fair value and a change in the assumption used for weighted average cost of capital or volatility would result in a directionally opposite change in the fair value. The determination of the fair values of investments, where the Company is a minority shareholder and has access to limited information from the investee, reflects numerous assumptions that are subject to various risks and uncertainties, including key assumptions regarding the investee’s expected growth rates and operating margin, expected length and severity of the impact from the COVID-19 pandemic and the shape and timing of the subsequent recovery, as well as other key assumptions with respect to matters outside of the Company's control, such as discount rates and market comparables. It requires significant judgments and estimates and actual results could be materially different than those judgments and estimates utilized in the fair value estimate. Future events and changing market conditions may lead the Company to re-evaluate the assumptions reflected in the valuation, particularly the assumptions related to the length and severity of the COVID-19 pandemic and the shape and timing of the subsequent recovery and the overall impact on the investee’s business, which may result in a need to recognize an additional impairment charge that could have a material adverse effect on the Company's results of operations. Derivatives The Company's derivative instruments are valued using pricing models. Pricing models take into account the contract terms as well as multiple inputs where applicable, such as interest rate yield curves, option volatility and foreign currency exchange rates. The valuation of derivatives are considered "Level 2 " fair value measurements. The Company's derivative instruments are typically short-term in nature. In the normal course of business, the Company is exposed to the impact of foreign currency fluctuations. The Company mitigates these risks by following established risk management policies and procedures, including the use of derivatives. The Company enters into foreign currency derivative contracts to hedge translation risks from short-term foreign currency exchange rate fluctuations for the Euro, British Pound Sterling and certain other currencies versus the U.S. Dollar. The Company also enters into foreign currency forward contracts to hedge its exposure to the impact of movements in foreign currency exchange rates on its transactional balances denominated in currencies other than the functional currency. The Company does not use derivatives for trading or speculative purposes. The Company reports the fair values of its derivative assets and liabilities on a gross basis in the Consolidated Balance Sheets in "Prepaid expenses and other current assets, net" and "Accrued expenses and other current liabilities," respectively. Unless designated as hedges for accounting purposes, gains and losses resulting from changes in the fair values of derivative instruments are recognized in "Foreign currency transactions and other" in the Unaudited Consolidated Statements of Operations in the period that the changes occur and cash flow impacts, if any, are classified within "Net cash (used in) provided by operating activities" in the Unaudited Consolidated Statements of Cash Flows. As of March 31, 2020 and December 31, 2019, the Company did not designate any derivatives as hedges for accounting purposes. The table below provides fair values and notional amounts of foreign currency exchange derivatives outstanding at March 31, 2020 and December 31, 2019 (in millions). The notional amount of a foreign currency forward contract is the contracted amount of foreign currency to be exchanged and is not recorded in the balance sheets. March 31, 2020 December 31, 2019 Fair value of derivative assets $ 12 $ 12 Fair value of derivative liabilities 21 5 Notional amount: Foreign currency purchases 1,441 1,770 Foreign currency sales 950 901 The effect of foreign currency exchange derivatives recorded in " Foreign currency transactions and other " in the Unaudited Consolidated Statements of Operations for the three months ended March 31, 2020 and 2019 is as follows (in millions): For the Three Months Ended March 31, 2020 March 31, 2019 Losses on foreign currency exchange derivatives $ 23 $ 13 Other Financial Assets and Liabilities At March 31, 2020 and December 31, 2019 , the Company's cash consisted of bank deposits. Other financial assets and liabilities, including restricted cash, accounts payable, accrued expenses and deferred merchant bookings, are carried at cost which approximates their fair values because of the short-term nature of these items. Accounts receivable and other financial assets measured at amortized cost are carried at cost less an allowance for expected credit losses to present the net amount expected to be collected (see Note 7 ). See Note 9 for the estimated fair value of the Company's outstanding senior notes and Note 5 for information related to an embedded derivative associated with the $25 million Trip.com Group convertible notes issued in 2016. Goodwill See Note 8

ACCOUNTS RECEIVABLE AND OTHER F

ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS (Notes)	3 Months Ended
	Mar. 31, 2020
Accounts Receivable [Abstract]
ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS	ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS Accounts receivable in the Consolidated Balance Sheets at March 31, 2020 and December 31, 2019 includes receivables from customers of $740 million and $1.2 billion , respectively, and receivables from marketing affiliates of $61 million and $110 million , respectively. The remaining balance relates to receivables from third-party payment processors. The Company’s receivables are short-term in nature. In addition, the Company had prepayments to certain customers of $104 million and $232 million at March 31, 2020 and December 31, 2019, respectively, which are included in "Prepaid expenses and other current assets, net," and $126 million at March 31, 2020 , which is included in "Other assets, net" in the Consolidated Balance Sheets. The amounts mentioned above are stated on a gross basis, before deducting the allowance for expected credit losses. For periods prior to January 1, 2020, receivables from customers were recorded at the original invoiced amounts net of an allowance for doubtful accounts. On January 1, 2020, the Company adopted the accounting standards update on the measurement of credit losses, which requires the Company to estimate lifetime expected credit losses upon recognition of the financial assets. The Company adopted the accounting standards update using a modified retrospective approach and the adoption did not have a material impact to the Company's Unaudited Consolidated Financial Statements. The Company has identified the following risk characteristics of its customers and the related receivables and prepayments: size, type (alternative accommodations vs. hotels) or geographic location of the customer, or a combination of these characteristics. Receivables with similar risk characteristics have been grouped into pools. For each pool, the Company considers the historical credit loss experience, current economic conditions, supportable forecasts of future economic conditions, and any recoveries in assessing the lifetime expected credit losses. Other key factors that influence the expected credit loss analysis include customer demographics, payment terms offered in the normal course of business to customers, the nature of competition, and industry-specific factors that could impact the Company's receivables. Additionally, external data and macroeconomic factors are considered. This is assessed at each quarter based on the Company’s specific facts and circumstances. The following table summarizes the activity of the allowance for expected credit losses on receivables (in millions): For the Three Months Ended 2020 2019 Balance, beginning of year $ 49 $ 51 Provision charged to earnings 199 17 Write-offs and adjustments (1 ) (18 ) Currency translation adjustments (2 ) (1 ) Balance, end of period $ 245 $ 49 The allowance for expected credit losses on receivables as of March 31, 2020 includes a portion of the amounts related to refunds paid or payable to certain travelers without a corresponding estimated expected recovery from the travel service providers (see Note 2). For the three months ended March 31, 2020, the Company recorded a reduction in revenue of $48 million for such refunds, which is included in "Provision charged to earnings" in the table above. In addition, the Company recorded an allowance for expected credit loss on prepayments to certain customers of $54 million and $6 million at March 31, 2020 and December 31, 2019, respectively, which are included in "Prepaid expenses and other current assets, net" and "Other assets, net" in the Consolidated Balance Sheets. Due to the impact of the COVID-19 pandemic (see Note 1 ), given the volatility in global markets and the financial difficulties faced by many of the Company’s travel service provider and restaurant customers and marketing affiliates, the Company has increased its allowance for expected credit losses on receivables from and prepayments to its customers and marketing affiliates. For the three months ended March 31, 2020, the Company recorded additional expected credit loss expenses of $183 million , which is included in "Sales and other expenses" in the Unaudited Consolidated Statement of Operations. Significant judgments and assumptions are required to estimate the allowance for expected credit losses on receivables from and prepayments to customers and such assumptions may change in future periods, particularly the assumptions related to the impact of the COVID-19 pandemic on the business prospects and financial condition of customers and the Company’s ability to collect the receivable or recover the prepayment.

INTANGIBLE ASSETS AND GOODWILL

INTANGIBLE ASSETS AND GOODWILL	3 Months Ended
	Mar. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
INTANGIBLE ASSETS AND GOODWILL	GOODWILL, INTANGIBLE ASSETS AND OTHER LONG-LIVED ASSETS A substantial portion of the Company’s intangible assets and goodwill relates to the acquisitions of OpenTable and KAYAK. Goodwill The changes in the balance of goodwill for the three months ended March 31, 2020 consist of the following (in millions): Balance, December 31, 2019 (1) $ 2,913 Impairment (489 ) Foreign currency translation adjustments (33 ) Balance, March 31, 2020 (1) $ 2,391 (1) The balance of goodwill as of March 31, 2020 and December 31, 2019 is stated net of cumulative impairment charges of $1.4 billion and $941 million , respectively. The Company tests goodwill for impairment annually and whenever an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. The Company tests goodwill at a reporting unit level. The Company’s annual goodwill impairments tests are performed as of September 30. Due to the significant and negative financial impact of the COVID-19 pandemic (see Note 1 ), the Company performed an interim period goodwill impairment test at March 31, 2020. Under the current goodwill impairment standard adopted in the first quarter of 2020, a goodwill impairment loss is measured at the amount by which a reporting unit’s carrying amount exceeds its fair value, not to exceed the carrying amount of goodwill (see Note 1 ). As of March 31, 2020, the fair value of each of the Company’s reporting units, except the OpenTable and KAYAK reporting unit, exceeded its respective carrying value. For the OpenTable and KAYAK reporting unit, the Company recognized a goodwill impairment charge of $489 million , which is not tax-deductible, resulting in an adjusted carrying value of goodwill for OpenTable and KAYAK of $1.5 billion at March 31, 2020. The goodwill impairment was primarily driven by a significant reduction in the forecasted near-term cash flows of OpenTable and KAYAK as well as the significant decline in comparable companies' market values as a result of the COVID-19 pandemic. The estimated fair value of OpenTable and KAYAK was determined using a combination of standard valuation techniques, including an income approach (discounted cash flows) and a market approach (applying the recent decline in enterprise values of comparable publicly-traded companies to the recently calculated fair value for OpenTable and KAYAK, as well as applying comparable company multiples). The income approach estimates fair value utilizing long-term growth rates and discount rates applied to the cash flow projection. In the cash flow projection, the Company assumes that OpenTable and KAYAK will experience a significant decline in near-term cash flows with a recovery to 2019 levels of financial performance occurring in 2023. The shape and timing of the recovery is a key assumption in the fair value calculation (both in the income and market approaches), however, it is highly uncertain whether the actual recovery will match the trajectory or magnitude of the Company's assumptions. If the timing of recovery to 2019 levels of financial performance were to occur in 2022 or 2024, the impact to the estimated fair value, at March 31, 2020, ranges from an increase of over $230 million to a decrease of over $410 million . The estimation of fair value reflects numerous assumptions that are subject to various risks and uncertainties, including key assumptions regarding OpenTable and KAYAK’s expected growth rates and operating margin, expected length and severity of the impact from the COVID-19 pandemic and the shape and timing of the subsequent recovery, as well as other key assumptions with respect to matters outside of the Company's control, such as discount rates and market comparables. It requires significant judgments and estimates and actual results could be materially different than the judgments and estimates used to estimate fair value. Future events and changing market conditions may lead the Company to re-evaluate the assumptions reflected in the current forecast disclosed above, particularly the assumptions related to the length and severity of the COVID-19 pandemic and the shape and timing of the subsequent recovery, which may result in a need to recognize an additional goodwill impairment charge, which could have a material adverse effect on the Company's results of operations. Intangible Assets and Other Long-lived Assets The Company's intangible assets at March 31, 2020 and December 31, 2019 consist of the following (in millions): March 31, 2020 December 31, 2019 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Amortization Supply and distribution agreements $ 1,083 $ (478 ) $ 605 $ 1,100 $ (472 ) $ 628 3 - 20 years Technology 169 (131 ) 38 170 (129 ) 41 2 - 7 years Internet domain names 39 (32 ) 7 40 (32 ) 8 5 - 20 years Trade names 1,802 (555 ) 1,247 1,811 (534 ) 1,277 4 - 20 years Other intangible assets 2 (2 ) — 2 (2 ) — Up to 15 years Total intangible assets $ 3,095 $ (1,198 ) $ 1,897 $ 3,123 $ (1,169 ) $ 1,954 Intangible assets are amortized on a straight-line basis. Amortization expense was $43 million and $45 million for the three months ended March 31, 2020 and March 31, 2019 , respectively. The Company reviews long-lived assets, including intangible assets and operating lease assets, whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. The assessment of possible impairment is based upon the ability to recover the carrying value of the assets from the estimated undiscounted future net cash flows, before interest and taxes, of the related asset group. Due to the significant and negative financial impact of the COVID-19 pandemic (see Note 1

DEBT

DEBT	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
DEBT	DEBT Revolving Credit Facility In August 2019, the Company entered into a $2.0 billion five -year unsecured revolving credit facility with a group of lenders. Borrowings under the revolving credit facility will bear interest, at the Company’s option, at a rate per annum equal to either (i) the London Inter-bank Offer Rate, or if such London Inter-bank Offer Rate is no longer available, the agreed alternate rate of interest ("LIBOR") (but no less than 0% ) for the interest period in effect for such borrowing plus an applicable margin ranging from 0.875% to 1.50% ; or (ii) for U.S. Dollar-denominated loans only, the sum of (x) the greatest of (a) JPMorgan Chase Bank, N.A.'s prime lending rate, (b) the U.S. federal funds rate plus 0.50% and (c) LIBOR (but no less than 0% ) for an interest period of one month plus 1.00% , plus (y) an applicable margin ranging from 0% to 0.50% . Undrawn balances available under the revolving credit facility are subject to commitment fees at the applicable rate ranging from 0.07% to 0.20% . The revolving credit facility provides for the issuance of up to $80 million of letters of credit as well as borrowings of up to $100 million on same-day notice, referred to as swingline loans. Other than swingline loans, which are available only in U.S. Dollars, borrowings and letters of credit under the revolving credit facility may be made in U.S. Dollars, Euros, British Pounds Sterling and any other foreign currency agreed to by the lenders. The proceeds of loans made under the facility can be used for working capital and general corporate purposes, including acquisitions, share repurchases and debt repayments. There were no borrowings outstanding and $5 million of letters of credit issued under this revolving credit facility at March 31, 2020 and December 31, 2019 . Upon entering into this revolving credit facility, the Company terminated its prior $2.0 billion five -year revolving credit facility entered into in June 2015. During the three months ended March 31, 2019, the Company made short-term borrowings under the prior revolving credit facility totaling $250 million with a weighted-average interest rate of 3.5% , which were repaid during the three months ended June 30, 2019. The current revolving credit facility contains a maximum leverage ratio covenant, compliance with which is a condition to the Company's ability to borrow thereunder. In April 2020, the Company amended the revolving credit facility, pursuant to which the maximum leverage ratio covenant has been suspended through and including the quarter ending March 31, 2021, and has been replaced with a minimum liquidity covenant based on unrestricted cash, cash equivalents, short-term investments and unused capacity under this revolving credit facility. Beginning with the quarter ending June 30, 2021, the minimum liquidity covenant will cease to apply and the maximum leverage ratio covenant will again be in effect. Outstanding Debt Outstanding debt at March 31, 2020 consists of the following (in millions): March 31, 2020 Outstanding Principal Amount Unamortized Debt Discount and Debt Issuance Cost Carrying Value Current liabilities: 0.35% Convertible Senior Notes due June 2020 $ 1,000 $ (5 ) $ 995 Long-term debt: 0.9% Convertible Senior Notes due September 2021 $ 1,000 $ (33 ) $ 967 0.8% (€1 Billion) Senior Notes due March 2022 1,097 (3 ) 1,094 2.15% (€750 Million) Senior Notes due November 2022 824 (2 ) 822 2.75% Senior Notes due March 2023 500 (2 ) 498 2.375% (€1 Billion) Senior Notes due September 2024 1,097 (8 ) 1,089 3.65% Senior Notes due March 2025 500 (2 ) 498 3.6% Senior Notes due June 2026 1,000 (5 ) 995 1.8% (€1 Billion) Senior Notes due March 2027 1,097 (4 ) 1,093 3.55% Senior Notes due March 2028 500 (3 ) 497 Total long-term debt $ 7,615 $ (62 ) $ 7,553 Outstanding debt at December 31, 2019 consists of the following (in millions): December 31, 2019 Outstanding Principal Amount Unamortized Debt Discount and Debt Issuance Cost Carrying Value Current Liabilities: 0.35% Convertible Senior Notes due June 2020 $ 1,000 $ (12 ) $ 988 Long-term debt: 0.9% Convertible Senior Notes due September 2021 1,000 (39 ) 961 0.8% (€1 Billion) Senior Notes due March 2022 1,123 (3 ) 1,120 2.15% (€750 Million) Senior Notes due November 2022 842 (3 ) 839 2.75% Senior Notes due March 2023 500 (2 ) 498 2.375% (€1 Billion) Senior Notes due September 2024 1,123 (9 ) 1,114 3.65% Senior Notes due March 2025 500 (2 ) 498 3.6% Senior Notes due June 2026 1,000 (5 ) 995 1.8% (€1 Billion) Senior Notes due March 2027 1,123 (5 ) 1,118 3.55% Senior Notes due March 2028 500 (3 ) 497 Total long-term debt $ 7,711 $ (71 ) $ 7,640 Based on the closing price of the Company's common stock for the prescribed measurement periods for the three months ended March 31, 2020 and December 31, 2019 , the contingent conversion thresholds on the 2020 Notes (as defined below) and 2021 Notes (as defined below) were not exceeded. The 2021 Notes were not convertible at the option of the holder at March 31, 2020 and December 31, 2019 . However, starting on March 15, 2020, the 2020 Notes became convertible at the option of the holder, regardless of the Company's stock price. At March 31, 2020 , the 2020 Notes are convertible at the option of the holders and the principal amount is required to be paid in cash. The Company reclassified the equity component in the amount of $4 million at March 31, 2020 , from additional paid-in-capital to convertible debt in the mezzanine section in the Company's Consolidated Balance Sheet. Fair Value of Debt At March 31, 2020 and December 31, 2019 , the estimated fair value of the outstanding Senior Notes was approximately $8.7 billion and $9.8 billion , respectively, and was considered a "Level 2 " fair value measurement (see Note 6 ). Fair value was estimated based upon actual trades at the end of the reporting period or the most recent trade available as well as the Company's stock price at the end of the reporting period. The fair value of the Company's debt in excess of the outstanding principal amount primarily relates to the conversion premium on the Convertible Senior Notes. Convertible Senior Notes If the note holders exercise their option to convert, the Company delivers cash to repay the principal amount of the notes and delivers shares of common stock or cash, at its option, to satisfy the conversion value in excess of the principal amount. If the Company's convertible debt is redeemed or converted prior to maturity, a gain or loss on extinguishment is recognized. The gain or loss is the difference between the fair value of the debt component immediately prior to extinguishment and its carrying value. To estimate the fair value of the debt at the conversion date, the Company estimates the borrowing rate, considering the credit rating and similar debt of comparable corporate issuers without the conversion feature. Description of Convertible Senior Notes In August 2014, the Company issued in a private placement $1.0 billion aggregate principal amount of Convertible Senior Notes due September 15, 2021, with an interest rate of 0.9% (the "2021 Notes"). The Company paid $11 million in debt issuance costs during the year ended December 31, 2014 related to this offering. The 2021 Notes are convertible, subject to certain conditions, into the Company's common stock at a conversion price of $2,055.50 per share. The 2021 Notes are convertible, at the option of the holder, prior to September 15, 2021, upon the occurrence of specific events, including but not limited to a change in control, or if the closing sales price of the Company's common stock for at least 20 trading days in the period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is more than 150% of the conversion price in effect for the notes on the last trading day of the immediately preceding quarter. In the event that all or substantially all of the Company's common stock is acquired on or prior to the maturity of the 2021 Notes in a transaction in which the consideration paid to holders of the Company's common stock consists of all or substantially all cash, the Company would be required to make additional payments in the form of additional shares of common stock to the holders of the 2021 Notes in an aggregate value ranging from $0 to $375 million depending upon the date of the transaction and the then current stock price of the Company. Starting on June 15, 2021, holders will have the right to convert all or any portion of the 2021 Notes, regardless of the Company's stock price. The 2021 Notes may not be redeemed by the Company prior to maturity. The holders may require the Company to repurchase the 2021 Notes for cash in certain circumstances. Interest on the 2021 Notes is payable on March 15 and September 15 of each year. At March 31, 2020, the if-converted value of the 2021 Notes did not exceed the aggregate principle amount. In May 2013, the Company issued in a private placement $1.0 billion aggregate principal amount of Convertible Senior Notes due June 15, 2020, with an interest rate of 0.35% (the "2020 Notes"). The 2020 Notes were issued with an initial discount of $20 million . The Company paid $1 million in debt issuance costs during the year ended December 31, 2013 related to this offering. The 2020 Notes are convertible, subject to certain conditions, into the Company's common stock at a conversion price of $1,315.10 per share. The 2020 Notes are convertible, at the option of the holder, prior to June 15, 2020, upon the occurrence of specific events, including but not limited to a change in control, or if the closing sales price of the Company's common stock for at least 20 trading days in the period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is more than 150% of the conversion price in effect for the notes on the last trading day of the immediately preceding quarter. In the event that all or substantially all of the Company's common stock is acquired on or prior to the maturity of the 2020 Notes in a transaction in which the consideration paid to holders of the Company's common stock consists of all or substantially all cash, the Company would be required to make additional payments in the form of additional shares of common stock to the holders of the 2020 Notes in an aggregate value ranging from $0 to $397 million depending upon the date of the transaction and the then current stock price of the Company. Since March 15, 2020, holders have had the right to convert all or any portion of the 2020 Notes, regardless of the Company's stock price. The 2020 Notes may not be redeemed by the Company prior to maturity. The holders may require the Company to repurchase the 2020 Notes for cash in certain circumstances. Interest on the 2020 Notes is payable on June 15 and December 15 of each year. At March 31, 2020, the if-converted value of the 2020 Notes exceeded the aggregate principle amount by $92 million . Cash-settled convertible debt, such as the Company's convertible senior notes, is separated into debt and equity components at issuance and each component is assigned a value. The value assigned to the debt component is the estimated fair value, at the issuance date, of a similar bond without the conversion feature. The difference between the bond cash proceeds and this estimated fair value, representing the value assigned to the equity component, is recorded as a debt discount. Debt discount is amortized using the effective interest rate method over the period from the origination date through the stated maturity date. The Company estimated the borrowing rates at debt origination to be 3.18% for the 2021 Notes and 3.13% for the 2020 Notes, considering its credit rating and similar debt of comparable corporate issuers without the conversion feature. The yield to maturity was estimated at an at-market coupon priced at par. Debt discount after tax of $83 million ( $143 million before tax) related to the 2021 Notes and $92 million ( $154 million before tax) related to the 2020 Notes less financing costs associated with the equity component of the respective convertible notes was recorded in "Additional paid-in capital" in the balance sheet at debt origination. For both the three months ended March 31, 2020 and 2019 , the Company recognized interest expense of $15 million related to convertible notes, which is almost entirely comprised of the amortization of debt discount of $12 million and the contractual coupon interest of $3 million for each period. For the three months ended March 31, 2020 and 2019 , included in the amortization of debt discount mentioned above is $1 million of original issuance discount related to the 2020 Notes for each period. The remaining interest expense relates to the amortization of debt issuance costs. The remaining period for amortization of debt discount and debt issuance costs is the period until the stated maturity date for the respective debt. The weighted-average effective interest rates for both the three months ended March 31, 2020 and 2019 were 3.2% . In April 2020, the Company issued a private placement of $863 million aggregate principal amount of Convertible Senior Notes due May 1, 2025 with an interest rate of 0.75% (the "May 2025 Notes"). The May 2025 Notes are convertible, subject to certain conditions, into the Company's common stock at a conversion price of $1,886.44 per share. The May 2025 Notes are convertible, at the option of the holder, prior to November 1, 2024, upon the occurrence of specific events, including but not limited to a change in control, or if the closing sales price of the Company's common stock for at least 20 trading days in the period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is more than 130% of the conversion price in effect for the notes on the last trading day of the immediate preceding quarter. In the event that all or substantially all of the Company's common stock is acquired on or prior to the maturity of the May 2025 Notes in a transaction in which the consideration paid to holders of the Company's common stock consists of all or substantially all cash, the Company would be required to make additional payments in the form of additional shares of common stock to the holders of the May 2025 Notes in an aggregate value ranging from $0 to $273 million depending upon the date of the transaction and the then current stock price of the Company. Starting on November 1, 2024, holders will have the right to convert all or any portion of the May 2025 Notes, regardless of the Company's stock price. The May 2025 Notes may not be redeemed by the Company prior to maturity. The holders may require the Company to repurchase the May 2025 Notes for cash in certain circumstances. Interest on the May 2025 Notes is payable on May 1 and November 1 of each year, beginning on November 1, 2020. The proceeds from the issuance of the May 2025 Notes can be used for general corporate purposes, which may include repayment of debt, including the repayment, at maturity or upon conversion prior thereto, of the Company’s 2020 Notes and 2021 Notes. Other Long-term Debt Other long-term debt had a total carrying value of $6.6 billion and $6.7 billion at March 31, 2020 and December 31, 2019 , respectively. Debt discount is amortized using the effective interest rate method over the period from the origination date through the stated maturity date. The following table summarizes the information related to other long-term debt at March 31, 2020 : Other Long-term Debt Period of Issuance Effective Interest Rate at Debt Origination Timing of Interest Payments 0.8% Senior Notes due March 2022 March 2017 0.84 % Annually in March 2.15% Senior Notes due November 2022 November 2015 2.20 % Annually in November 2.75% Senior Notes due March 2023 August 2017 2.78 % Semi-annually in March and September 2.375% Senior Notes due September 2024 September 2014 2.48 % Annually in September 3.65% Senior Notes due March 2025 March 2015 3.68 % Semi-annually in March and September 3.6% Senior Notes due June 2026 May 2016 3.62 % Semi-annually in June and December 1.8% Senior Notes due March 2027 March 2015 1.80 % Annually in March 3.55% Senior Notes due March 2028 August 2017 3.56 % Semi-annually in March and September For both the three months ended March 31, 2020 and 2019 , the Company recognized interest expense of $42 million related to other long-term debt, which is almost entirely comprised of $40 million related to the contractual coupon interest for each period. The remaining interest expense relates to the amortization of debt discount and debt issuance costs. The remaining period for amortization of debt discount and debt issuance costs is the period until the stated maturity dates for the respective debt. Historically, the aggregate principal value of the Euro-denominated Senior Notes maturing in March 2022, November 2022, September 2024 and March 2027 (collectively the "Euro-denominated debt") and accrued interest thereon had been designated as a hedge of the Company's net investment in a Euro functional currency subsidiary. Beginning in the second quarter of 2019, the Company has only designated certain portions of the aggregated principal value of the Euro-denominated debt as a hedge. For the three months ended March 31, 2020 , the carrying value of the portion of Euro-denominated debt designated as a net investment hedge ranged from $2.1 billion to $3.2 billion . The foreign currency transaction gains or losses on these Euro-denominated liabilities are measured based upon changes in spot rates. The foreign currency transaction gains or losses on the Euro-denominated debt that is designated as a hedging instrument for accounting purposes are recorded in " Accumulated other comprehensive loss " in the Consolidated Balance Sheets. The net assets of this Euro functional currency subsidiary are translated into U.S. Dollars at each balance sheet date, with the effects of foreign currency changes also reported in " Accumulated other comprehensive loss " in the Consolidated Balance Sheets. The foreign currency transaction gains or losses on the Euro-denominated debt that is not designated as a hedging instrument are recognized in " Foreign currency transactions and other " in the Unaudited Consolidated Statements of Operations. In April 2020, the Company issued Senior Notes due April 13, 2025 with an interest rate of 4.10% for an aggregate principal amount of $1 billion , Senior Notes due April 13, 2027 with an interest rate of 4.50% for an aggregate principal amount of $750 million and Senior Notes due April 13, 2030 with an interest rate of 4.625% for an aggregate principal amount of $1.5 billion . Interest on these Senior Notes is payable on April 13 and October 13 of each year, beginning on October 13, 2020. The proceeds from the issuance of the Senior Notes can be used for general corporate purposes, which may include repayment of debt, including the repayment, at maturity or upon conversion prior thereto, of the Company’s 2020 Notes and 2021 Notes.

TREASURY STOCK

TREASURY STOCK	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
TREASURY STOCK	TREASURY STOCK At December 31, 2019, the Company had a total remaining authorization of $11.5 billion to repurchase its common stock related to a program authorized by the Company's Board of Directors in 2019 for $15.0 billion . At March 31, 2020 , the Company had a total remaining authorization of $10.4 billion to repurchase its common stock. The Company has not repurchased any shares in the second quarter of 2020 and does not intend to initiate any repurchases until it has better visibility into the shape and timing of a recovery from the COVID-19 pandemic. Additionally, the Board of Directors has given the Company the general authorization to repurchase shares of its common stock withheld to satisfy employee withholding tax obligations related to stock-based compensation. The following table summarizes the Company's stock repurchase activities during the three months ended March 31, 2020 and 2019 (in millions, except for shares, which are reflected in thousands): Three Months Ended Three Months Ended Shares Amount Shares Amount Authorized stock repurchase programs 601 $ 1,122 1,548 $ 2,735 General authorization for shares withheld on stock award vesting 77 129 71 121 Total 678 $ 1,251 1,619 $ 2,856 Stock repurchases of $40 million in December 2019 were settled in January 2020. For the three months ended March 31, 2020 and 2019 , the Company remitted employee withholding taxes of $119 million and $111 million , respectively, to the tax authorities, which is different from the aggregate cost of the shares withheld for taxes for each period due to the timing in remitting the taxes. The cash remitted to the tax authorities is included in financing activities in the Unaudited Consolidated Statements of Cash Flows. At March 31, 2020 , there were 22,439,549 shares of the Company's common stock held in treasury.

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES Income tax expense consists of U.S. and international income taxes, determined using an estimate of the Company's annual effective tax rate, which is based upon the applicable tax rates and tax laws of the countries in which the income is generated. A deferred tax liability is recognized for all taxable temporary differences, and a deferred tax asset is recognized for all deductible temporary differences and operating loss and tax credit carryforwards. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized. The Company considers many factors when assessing the likelihood of future realization of the deferred tax assets, including its recent cumulative earnings experience by taxing jurisdiction, expectations of future income, tax planning strategies, the carryforward periods available for tax reporting purposes and other relevant factors. The Company's effective tax rate for the three months ended March 31, 2020 was 3.1% , compared to 21.0% for the three months ended March 31, 2019 . The Company's 2020 effective tax rate differs from the U.S. federal statutory tax rate of 21% , and was lower for the three months ended March 31, 2020, compared to the three months ended March 31, 2019, primarily due to the non-deductible goodwill impairment charge related to OpenTable and KAYAK and valuation allowances recorded against the deferred tax assets generated from the impairment of a long-term investment. During the three months ended March 31, 2019 , a majority of the Company's income was reported in the Netherlands, where Booking.com is based. According to Dutch corporate income tax law, income generated from qualifying innovative activities is taxed at a rate of 7% ("Innovation Box Tax") rather than the Dutch statutory rate of 25% . A portion of Booking.com's earnings during the three months ended March 31, 2019 qualified for Innovation Box Tax treatment, which had a beneficial impact on the Company's effective tax rate for that period. During the three months ended March 31, 2020 , the Company did not benefit from the Innovation Box Tax.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME	3 Months Ended
	Mar. 31, 2020
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
ACCUMULATED OTHER COMPREHENSIVE INCOME	CHANGES IN ACCUMULATED OTHER COMPREHENSIVE LOSS BY COMPONENT The tables below present the changes in the balances of accumulated other comprehensive loss ("AOCl") by component for the three months ended March 31, 2020 and 2019 (in millions): Foreign currency translation adjustments, net of tax Net unrealized (losses) gains on available-for-sale securities, net of tax Total AOCI, net of tax Foreign currency translation Net Investment Hedges (1) Total, net of tax Before tax Tax (expense) benefit Total, net of tax Before tax Tax benefit (2) Before tax Tax expense Balance, December 31, 2019 $ (186 ) $ 54 $ (2 ) $ (5 ) (139 ) $ (7 ) $ (45 ) (52 ) (191 ) Other Comprehensive (Loss) Income ("OCI") before reclassifications (128 ) 4 62 (15 ) (77 ) (94 ) 17 (77 ) (154 ) Amounts reclassified to (3) — — — — — 4 (1 ) 3 3 OCI for the period (128 ) 4 62 (15 ) (77 ) (90 ) 16 (74 ) (151 ) Balance, March 31, 2020 $ (314 ) $ 58 $ 60 $ (20 ) $ (216 ) $ (97 ) $ (29 ) $ (126 ) $ (342 ) Foreign currency translation adjustments, net of tax Net unrealized (losses) gains on available-for-sale securities, net of tax Total AOCI, net of tax Foreign currency translation Net Investment Hedges (1) Total, net of tax Before tax Tax expense Total, net of tax Before tax Tax benefit (2) Before tax Tax benefit (expense) Balance, December 31, 2018 $ (109 ) $ 41 $ (73 ) $ 12 (129 ) $ (157 ) $ (30 ) (187 ) (316 ) OCI before reclassifications (80 ) 11 76 (19 ) (12 ) 211 (51 ) 160 148 Amounts reclassified to net income (3) — — — — — (1 ) — (1 ) (1 ) OCI for the period (80 ) 11 76 (19 ) (12 ) 210 (51 ) 159 147 Balance, March 31, 2019 $ (189 ) $ 52 $ 3 $ (7 ) $ (141 ) $ 53 $ (81 ) $ (28 ) $ (169 ) (1) Net investment hedges balance, net of tax, at March 31, 2020 and earlier dates presented above, include accumulated net losses from fair value adjustments of $35 million after tax ( $53 million before tax) associated with previously settled derivatives that were designated as net investment hedges. The remaining balances relate to foreign currency transaction gains (losses) and related tax benefits (expenses) associated with the Company's Euro-denominated debt that is designated as a hedge against the impact of currency fluctuations on the net assets of a Euro functional currency subsidiary (see Note 9 ). (2) The tax benefits relate to foreign currency translation adjustments to the Company's one-time deemed repatriation tax liability recorded at December 31, 2017 and foreign earnings for periods after December 31, 2017 that are subject to U.S. federal and state income tax, resulting from the enactment of the U.S. Tax Cuts and Jobs Act (the "Tax Act"). (3) The reclassified net realized losses before tax from sales of investments in debt securities and impairment losses before tax related to debt securities held by the Company are included in "Foreign currency transactions and other" and the related reclassified tax benefits are included in " Income tax (benefit) expense " in the Unaudited Consolidated Statements of Operations. The cost of marketable debt securities sold is determined using a first-in and first-out method.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES

OTHER

OTHER	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
OTHER	OTHER Restricted Cash and Cash Equivalents Restricted cash and cash equivalents at March 31, 2020 and December 31, 2019 principally relates to the minimum cash requirement for the Company's travel-related insurance business. The following table reconciles cash and cash equivalents and restricted cash and cash equivalents reported in the Consolidated Balance Sheets to the total amounts shown in the Unaudited Consolidated Statements of Cash Flows (in millions): March 31, December 31, (Unaudited) As included in the Consolidated Balance Sheets: Cash and cash equivalents $ 6,363 $ 6,312 Restricted cash and cash equivalents included in "Prepaid expenses and other current assets, net" 20 20 Total cash and cash equivalents and restricted cash and cash equivalents as shown in the Unaudited Consolidated Statements of Cash Flows $ 6,383 $ 6,332 Income Taxes Prepayment and Refund In the first quarter of 2020, the Company made a prepayment of the Netherlands income taxes of $717 million to earn prepayment discounts, which were included in the “Prepaid expense and other current assets, net” in the Consolidated Balance Sheet at March 31, 2020. The Company requested a refund of this amount from the Dutch tax authorities and it was received in April 2020.

BASIS OF PRESENTATION (Policies

BASIS OF PRESENTATION (Policies)	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Management of Booking Holdings Inc. (the "Company") is responsible for the Unaudited Consolidated Financial Statements included in this document. The Unaudited Consolidated Financial Statements have been prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") and include all normal and recurring adjustments that management of the Company considers necessary for a fair presentation of its financial position and operating results. The Company prepared the Unaudited Consolidated Financial Statements following the requirements of the Securities and Exchange Commission for interim reporting. As permitted under those rules, the Company condensed or omitted certain footnotes or other financial information that are normally required by GAAP for annual financial statements. These statements should be read in combination with the Consolidated Financial Statements in the Company's Annual Report on Form 10-K for the year ended December 31, 2019 . The Unaudited Consolidated Financial Statements include the accounts of the Company and its wholly-owned subsidiaries. All inter-company accounts and transactions have been eliminated in consolidation. The functional currency of the Company's subsidiaries is generally the respective local currency. For international operations, assets and liabilities are translated into U.S. Dollars at the rate of exchange existing at the balance sheet date. Income statement amounts are translated at monthly average exchange rates applicable for the period. Translation gains and losses are included as a component of " Accumulated other comprehensive loss " in the accompanying Consolidated Balance Sheets. Foreign currency transaction gains and losses are included in "Foreign currency transactions and other" in the Unaudited Consolidated Statements of Operations. Revenues, expenses, assets and liabilities can vary during each quarter of the year. Therefore, the results and trends in these interim financial statements may not be the same as those for any subsequent quarter or the full year, especially during the periods that are impacted by the COVID-19 pandemic.
Change in Presentation and Reclassification	Change in Presentation and Reclassification In the year ended December 31, 2019 and prior periods, the Company's marketing expenses were presented in the Consolidated Statements of Operations as "Performance marketing" and "Brand marketing" expenses. In the first quarter of 2020, the Company changed the presentation of marketing expenses by combining "Performance marketing" and "Brand marketing" into "Marketing expenses" in the Unaudited Consolidated Statement of Operations because of the increased convergence of performance marketing and brand marketing channels in areas including digital marketing and the Company's view of overall marketing expenditure as its investment in customer acquisition and retention. The change in presentation had no impact on operating income or net income. The Unaudited Statement of Operations for the three months ended March 31, 2019 has been recast to conform to the current year presentation. In addition to the change in presentation for marketing expenses, certain amounts from prior periods have been reclassified to conform to the current period presentation.
Recent Accounting Pronouncements Adopted	Recent Accounting Pronouncements Adopted Simplifying the Test for Goodwill Impairment In January 2017, the Financial Accounting Standards Board ("FASB") issued a new accounting update to simplify the test for goodwill impairment. The revised guidance eliminates the previously required step two of the goodwill impairment test, which required a hypothetical purchase price allocation to measure goodwill impairment. Under the revised guidance, a goodwill impairment loss will be measured at the amount by which a reporting unit’s carrying amount exceeds its fair value, not to exceed the carrying amount of goodwill. The Company adopted this update in the first quarter of 2020 and applied it on a prospective basis (see Note 8 for further information on the goodwill impairment test performed at March 31, 2020). Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued a new accounting update on the measurement of credit losses for certain financial assets measured at amortized cost and available-for-sale debt securities. For financial assets measured at amortized cost, this update requires an entity to (1) estimate its lifetime expected credit losses upon recognition of the financial assets and establish an allowance to present the net amount expected to be collected, (2) recognize this allowance and changes in the allowance during subsequent periods through net income and (3) consider relevant information about past events, current conditions and reasonable and supportable forecasts in assessing the lifetime expected credit losses. For available-for-sale debt securities, this update made several targeted amendments to the existing other-than-temporary impairment model, including (1) requiring disclosure of the allowance for credit losses, (2) allowing reversals of the previously recognized credit losses until the entity has the intent to sell, is more-likely-than-not required to sell the securities or the maturity of the securities, (3) limiting impairment to the difference between the amortized cost basis and fair value and (4) not allowing entities to consider the length of time that fair value has been less than amortized cost as a factor in evaluating whether a credit loss exists. The Company adopted this update in the first quarter of 2020 and applied this update on a modified retrospective basis. Upon adoption of the new standard on January 1, 2020, the Company recorded a net decrease to its retained earnings of $3 million , net of tax. See Note 7 for further information related to allowance for expected credit losses on accounts receivable and other financial assets and Note 5 for further information related to investments in available-for-sale debt securities.
Other Recent Accounting Pronouncement(s)	Other Recent Accounting Pronouncement Simplifying the Accounting for Income Taxes In December 2019, the FASB issued a new accounting update relating to income taxes. This update provides an exception to the general methodology for calculating income taxes in an interim period when a year-to-date loss exceeds the anticipated loss for the year. This update also (1) requires an entity to recognize a franchise tax (or similar tax) that is partially based on income as an income-based tax and account for any incremental amount incurred as a non-income-based tax, (2) requires an entity to evaluate when a step-up in the tax basis of goodwill should be considered part of the business combination in which goodwill was originally recognized for accounting purposes and when it should be considered a separate transaction, and (3) requires that an entity reflect the effect of an enacted change in tax laws or rates in the annual effective tax rate computation in the interim period that includes the enactment date.

REVENUE (Tables)

REVENUE (Tables)	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Geographic Information	The Company's geographic information is as follows (in millions): International United States The Netherlands Other Total Total revenues for the three months ended March 31, 2020 $ 285 $ 1,677 $ 326 $ 2,288 2019 (1) 366 2,072 399 2,837
Activity of Deferred Revenue for Online Travel Reservation Services	The following table summarizes the activity of deferred revenue for online travel reservation services for the three months ended March 31, 2020 (in millions): Balance, December 31, 2019 $ 220 Revenues recognized from the beginning deferred revenue balance (150 ) Cancellations (46 ) Payments received from travelers, net of amounts estimated to be payable to travel service providers, and other 120 Balance, March 31, 2020 $ 144

STOCK-BASED EMPLOYEE COMPENSA_2

STOCK-BASED EMPLOYEE COMPENSATION (Tables)	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Activity of unvested restricted stock units	The following table summarizes the activity of restricted stock units for employees and non-employee directors during the three months ended March 31, 2020 : Restricted Stock Units Shares Weighted-average Grant-date Fair Value Per Share Unvested at December 31, 2019 256,745 $ 1,801 Granted 152,832 $ 1,732 Vested (109,595 ) $ 1,808 Forfeited (5,971 ) $ 1,805 Unvested at March 31, 2020 294,011 $ 1,762
Activity of unvested performance share units	The following table summarizes the activity of performance share units for employees during the three months ended March 31, 2020 : Performance Share Units Shares Weighted-average Grant-date Fair Value Per Share Unvested at December 31, 2019 216,083 $ 1,835 Vested (80,266 ) $ 1,737 Performance Shares Adjustment * (58,427 ) $ 1,957 Forfeited (2,989 ) $ 1,834 Unvested at March 31, 2020 74,401 $ 1,841
Estimated vesting of performance share units granted [Table Text Block]	The following table summarizes the estimated vesting, as of March 31, 2020 , of performance share units granted in 2019 and 2018 , net of forfeiture and vesting since the respective grant dates: Performance Share Units, by grant year 2019 2018 Shares probable to be issued 45,361 29,040 Shares not subject to the achievement of minimum performance thresholds 45,361 28,647 Shares that could be issued if maximum performance thresholds are met 117,558 79,914
Activity of outstanding stock options	All outstanding employee stock options were assumed in acquisitions, and generally have a term of 10 years from the grant date. The following table summarizes the activity for stock options during the three months ended March 31, 2020 : Employee Stock Options Number of Shares Weighted-average Aggregate Intrinsic Value (in millions) Weighted-average Remaining Contractual Term Balance, December 31, 2019 15,122 $ 484 $ 24 2.6 Exercised (100 ) $ 334 Balance, March 31, 2020 15,022 $ 485 $ 13 2.4 Vested and exercisable at March 31, 2020 15,022 $ 485 $ 13 2.4

NET INCOME PER SHARE (Tables)

NET INCOME PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Reconciliation of the weighted average number of shares outstanding used in calculating diluted earnings per share	A reconciliation of the weighted-average number of shares outstanding used in calculating diluted net (loss) income per share is as follows (in thousands): Three Months Ended 2020 2019 Weighted-average number of basic common shares outstanding 41,093 45,007 Weighted-average dilutive stock options, restricted stock units and performance share units — 229 Assumed conversion of convertible senior notes — 200 Weighted-average number of diluted common and common equivalent shares outstanding 41,093 45,436

INVESTMENTS (Tables)

INVESTMENTS (Tables)	3 Months Ended
	Mar. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Investment [Table Text Block]	The following table summarizes, by major security type, the Company's investments at March 31, 2020 (in millions): Cost Gross Unrealized Gains Gross Unrealized Losses Carrying Value Short-term investments: Debt securities: Corporate debt securities $ 164 $ — $ — $ 164 Trip.com Group convertible debt securities 250 — (2 ) 248 Equity securities: Trip.com Group equity securities 531 — (117 ) 414 Total $ 945 $ — $ (119 ) $ 826 Long-term investments: Investments in private companies: Debt securities $ 250 $ — $ (20 ) $ 230 Equity securities 501 — (100 ) 401 Other long-term investments: Debt securities: Trip.com Group convertible debt securities 525 — (77 ) 448 Equity securities 461 522 (6 ) 977 Total $ 1,737 $ 522 $ (203 ) $ 2,056 The following table summarizes, by major security type, the Company's investments at December 31, 2019 (in millions): Cost Gross Unrealized Gains Gross Unrealized Losses Carrying Value Short-term investments: Debt securities: International government securities $ 109 $ — $ — $ 109 U.S. government securities 138 — — 138 Corporate debt securities 751 1 (1 ) 751 Total $ 998 $ 1 $ (1 ) $ 998 Long-term investments: Investments in private companies: Debt securities $ 250 $ — $ — $ 250 Equity securities 501 — — 501 Other long-term investments: Debt securities: International government securities 68 — — 68 U.S. government securities 136 — (1 ) 135 Corporate debt securities 963 2 (2 ) 963 Trip.com Group convertible debt securities 775 — (8 ) 767 Equity securities 1,117 684 (8 ) 1,793 Total $ 3,810 $ 686 $ (19 ) $ 4,477

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Financial assets and liabilities carried at fair value	Financial assets and liabilities carried at fair value at March 31, 2020 are classified in the categories described in the table below (in millions): Level 1 Level 2 Level 3 Total Recurring fair value measurements ASSETS: Cash equivalents and restricted cash equivalents: Money market funds $ 5,944 $ — $ — $ 5,944 Time deposits and certificates of deposit 26 — — 26 Short-term investments: Corporate debt securities — 164 — 164 Trip.com Group convertible debt securities — 248 — 248 Trip.com Group equity securities 414 — — 414 Long-term investments: Investments in private companies: Debt securities — — 230 230 Other long-term investments: Trip.com Group convertible debt securities — 448 — 448 Equity securities 977 — — 977 Derivatives: Foreign currency exchange derivatives — 12 — 12 Total assets at fair value $ 7,361 $ 872 $ 230 $ 8,463 LIABILITIES: Foreign currency exchange derivatives $ — $ 21 $ — $ 21 Nonrecurring fair value measurements Investment in Didi Chuxing $ — $ — $ 400 $ 400 Goodwill of the OpenTable and KAYAK reporting unit — — 1,545 1,545 Total nonrecurring fair value measurements $ — $ — $ 1,945 $ 1,945 Financial assets and liabilities carried at fair value at December 31, 2019 are classified in the categories described in the table below (in millions): Level 1 Level 2 Level 3 Total Recurring fair value measurements ASSETS: Cash and restricted cash equivalents: Money market funds $ 5,734 $ — $ — $ 5,734 Corporate debt securities — 2 — 2 Time deposits and certificates of deposit 29 — — 29 Short-term investments: International government securities — 109 — 109 U.S. government securities — 138 — 138 Corporate debt securities — 751 — 751 Long-term investments: Investments in private companies: Debt securities — — 250 250 Other long-term investments: International government securities — 68 — 68 U.S. government securities — 135 — 135 Corporate debt securities — 963 — 963 Trip.com Group convertible debt securities — 767 — 767 Equity securities 1,793 — — 1,793 Derivatives: Foreign currency exchange derivatives — 12 — 12 Total assets at fair value $ 7,556 $ 2,945 $ 250 $ 10,751 LIABILITIES: Foreign currency exchange derivatives $ — $ 5 $ — $ 5
Rollforward of Level 3 fair value measurements	Rollforward of Level 3 Fair Value Measurements Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Debt securities (in millions) Balance, December 31, 2019 $ 250 Total losses for the period: Total unrealized losses included in accumulated other comprehensive loss (1) (20 ) Balance, March 31, 2020 $ 230 (1) These losses are recorded in “Accumulated other comprehensive loss” in the Consolidated Balance Sheet.
Fair value and notional amount of derivatives and the effect of foreign currency exchange derivatives	The table below provides fair values and notional amounts of foreign currency exchange derivatives outstanding at March 31, 2020 and December 31, 2019 (in millions). The notional amount of a foreign currency forward contract is the contracted amount of foreign currency to be exchanged and is not recorded in the balance sheets. March 31, 2020 December 31, 2019 Fair value of derivative assets $ 12 $ 12 Fair value of derivative liabilities 21 5 Notional amount: Foreign currency purchases 1,441 1,770 Foreign currency sales 950 901 The effect of foreign currency exchange derivatives recorded in " Foreign currency transactions and other " in the Unaudited Consolidated Statements of Operations for the three months ended March 31, 2020 and 2019 is as follows (in millions): For the Three Months Ended March 31, 2020 March 31, 2019 Losses on foreign currency exchange derivatives $ 23 $ 13

ACCOUNTS RECEIVABLE AND OTHER_2

ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS (Tables)	3 Months Ended
	Mar. 31, 2020
Accounts Receivable [Abstract]
Accounts Receivable, Allowance for Credit Loss [Table Text Block]	The following table summarizes the activity of the allowance for expected credit losses on receivables (in millions): For the Three Months Ended 2020 2019 Balance, beginning of year $ 49 $ 51 Provision charged to earnings 199 17 Write-offs and adjustments (1 ) (18 ) Currency translation adjustments (2 ) (1 ) Balance, end of period $ 245 $ 49

INTANGIBLE ASSETS AND GOODWILL

INTANGIBLE ASSETS AND GOODWILL (Tables)	3 Months Ended
	Mar. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill [Table Text Block]	The changes in the balance of goodwill for the three months ended March 31, 2020 consist of the following (in millions): Balance, December 31, 2019 (1) $ 2,913 Impairment (489 ) Foreign currency translation adjustments (33 ) Balance, March 31, 2020 (1) $ 2,391 (1) The balance of goodwill as of March 31, 2020 and December 31, 2019 is stated net of cumulative impairment charges of $1.4 billion and $941 million , respectively.
Intangible assets	The Company's intangible assets at March 31, 2020 and December 31, 2019 consist of the following (in millions): March 31, 2020 December 31, 2019 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Amortization Supply and distribution agreements $ 1,083 $ (478 ) $ 605 $ 1,100 $ (472 ) $ 628 3 - 20 years Technology 169 (131 ) 38 170 (129 ) 41 2 - 7 years Internet domain names 39 (32 ) 7 40 (32 ) 8 5 - 20 years Trade names 1,802 (555 ) 1,247 1,811 (534 ) 1,277 4 - 20 years Other intangible assets 2 (2 ) — 2 (2 ) — Up to 15 years Total intangible assets $ 3,095 $ (1,198 ) $ 1,897 $ 3,123 $ (1,169 ) $ 1,954

DEBT (Tables)

DEBT (Tables)	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Schedule Of Information Related To Other Long-Term Debt [Table Text Block]	The following table summarizes the information related to other long-term debt at March 31, 2020 : Other Long-term Debt Period of Issuance Effective Interest Rate at Debt Origination Timing of Interest Payments 0.8% Senior Notes due March 2022 March 2017 0.84 % Annually in March 2.15% Senior Notes due November 2022 November 2015 2.20 % Annually in November 2.75% Senior Notes due March 2023 August 2017 2.78 % Semi-annually in March and September 2.375% Senior Notes due September 2024 September 2014 2.48 % Annually in September 3.65% Senior Notes due March 2025 March 2015 3.68 % Semi-annually in March and September 3.6% Senior Notes due June 2026 May 2016 3.62 % Semi-annually in June and December 1.8% Senior Notes due March 2027 March 2015 1.80 % Annually in March 3.55% Senior Notes due March 2028 August 2017 3.56 % Semi-annually in March and September
Schedule of Debt	Outstanding debt at March 31, 2020 consists of the following (in millions): March 31, 2020 Outstanding Principal Amount Unamortized Debt Discount and Debt Issuance Cost Carrying Value Current liabilities: 0.35% Convertible Senior Notes due June 2020 $ 1,000 $ (5 ) $ 995 Long-term debt: 0.9% Convertible Senior Notes due September 2021 $ 1,000 $ (33 ) $ 967 0.8% (€1 Billion) Senior Notes due March 2022 1,097 (3 ) 1,094 2.15% (€750 Million) Senior Notes due November 2022 824 (2 ) 822 2.75% Senior Notes due March 2023 500 (2 ) 498 2.375% (€1 Billion) Senior Notes due September 2024 1,097 (8 ) 1,089 3.65% Senior Notes due March 2025 500 (2 ) 498 3.6% Senior Notes due June 2026 1,000 (5 ) 995 1.8% (€1 Billion) Senior Notes due March 2027 1,097 (4 ) 1,093 3.55% Senior Notes due March 2028 500 (3 ) 497 Total long-term debt $ 7,615 $ (62 ) $ 7,553 Outstanding debt at December 31, 2019 consists of the following (in millions): December 31, 2019 Outstanding Principal Amount Unamortized Debt Discount and Debt Issuance Cost Carrying Value Current Liabilities: 0.35% Convertible Senior Notes due June 2020 $ 1,000 $ (12 ) $ 988 Long-term debt: 0.9% Convertible Senior Notes due September 2021 1,000 (39 ) 961 0.8% (€1 Billion) Senior Notes due March 2022 1,123 (3 ) 1,120 2.15% (€750 Million) Senior Notes due November 2022 842 (3 ) 839 2.75% Senior Notes due March 2023 500 (2 ) 498 2.375% (€1 Billion) Senior Notes due September 2024 1,123 (9 ) 1,114 3.65% Senior Notes due March 2025 500 (2 ) 498 3.6% Senior Notes due June 2026 1,000 (5 ) 995 1.8% (€1 Billion) Senior Notes due March 2027 1,123 (5 ) 1,118 3.55% Senior Notes due March 2028 500 (3 ) 497 Total long-term debt $ 7,711 $ (71 ) $ 7,640

TREASURY STOCK (Tables)

TREASURY STOCK (Tables)	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Schedule of Stock Repurchase Activity	The following table summarizes the Company's stock repurchase activities during the three months ended March 31, 2020 and 2019 (in millions, except for shares, which are reflected in thousands): Three Months Ended Three Months Ended Shares Amount Shares Amount Authorized stock repurchase programs 601 $ 1,122 1,548 $ 2,735 General authorization for shares withheld on stock award vesting 77 129 71 121 Total 678 $ 1,251 1,619 $ 2,856

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE INCOME (Tables)	3 Months Ended
	Mar. 31, 2020
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Balances for each classification of accumulated other comprehensive income (loss)	The tables below present the changes in the balances of accumulated other comprehensive loss ("AOCl") by component for the three months ended March 31, 2020 and 2019 (in millions): Foreign currency translation adjustments, net of tax Net unrealized (losses) gains on available-for-sale securities, net of tax Total AOCI, net of tax Foreign currency translation Net Investment Hedges (1) Total, net of tax Before tax Tax (expense) benefit Total, net of tax Before tax Tax benefit (2) Before tax Tax expense Balance, December 31, 2019 $ (186 ) $ 54 $ (2 ) $ (5 ) (139 ) $ (7 ) $ (45 ) (52 ) (191 ) Other Comprehensive (Loss) Income ("OCI") before reclassifications (128 ) 4 62 (15 ) (77 ) (94 ) 17 (77 ) (154 ) Amounts reclassified to (3) — — — — — 4 (1 ) 3 3 OCI for the period (128 ) 4 62 (15 ) (77 ) (90 ) 16 (74 ) (151 ) Balance, March 31, 2020 $ (314 ) $ 58 $ 60 $ (20 ) $ (216 ) $ (97 ) $ (29 ) $ (126 ) $ (342 ) Foreign currency translation adjustments, net of tax Net unrealized (losses) gains on available-for-sale securities, net of tax Total AOCI, net of tax Foreign currency translation Net Investment Hedges (1) Total, net of tax Before tax Tax expense Total, net of tax Before tax Tax benefit (2) Before tax Tax benefit (expense) Balance, December 31, 2018 $ (109 ) $ 41 $ (73 ) $ 12 (129 ) $ (157 ) $ (30 ) (187 ) (316 ) OCI before reclassifications (80 ) 11 76 (19 ) (12 ) 211 (51 ) 160 148 Amounts reclassified to net income (3) — — — — — (1 ) — (1 ) (1 ) OCI for the period (80 ) 11 76 (19 ) (12 ) 210 (51 ) 159 147 Balance, March 31, 2019 $ (189 ) $ 52 $ 3 $ (7 ) $ (141 ) $ 53 $ (81 ) $ (28 ) $ (169 ) (1) Net investment hedges balance, net of tax, at March 31, 2020 and earlier dates presented above, include accumulated net losses from fair value adjustments of $35 million after tax ( $53 million before tax) associated with previously settled derivatives that were designated as net investment hedges. The remaining balances relate to foreign currency transaction gains (losses) and related tax benefits (expenses) associated with the Company's Euro-denominated debt that is designated as a hedge against the impact of currency fluctuations on the net assets of a Euro functional currency subsidiary (see Note 9 ). (2) The tax benefits relate to foreign currency translation adjustments to the Company's one-time deemed repatriation tax liability recorded at December 31, 2017 and foreign earnings for periods after December 31, 2017 that are subject to U.S. federal and state income tax, resulting from the enactment of the U.S. Tax Cuts and Jobs Act (the "Tax Act"). (3) The reclassified net realized losses before tax from sales of investments in debt securities and impairment losses before tax related to debt securities held by the Company are included in "Foreign currency transactions and other" and the related reclassified tax benefits are included in " Income tax (benefit) expense " in the Unaudited Consolidated Statements of Operations. The cost of marketable debt securities sold is determined using a first-in and first-out method.

OTHER (Tables)

OTHER (Tables)	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Reconciliation of Cash and Cash Equivalents and Restricted Cash and Cash Equivalents	The following table reconciles cash and cash equivalents and restricted cash and cash equivalents reported in the Consolidated Balance Sheets to the total amounts shown in the Unaudited Consolidated Statements of Cash Flows (in millions): March 31, December 31, (Unaudited) As included in the Consolidated Balance Sheets: Cash and cash equivalents $ 6,363 $ 6,312 Restricted cash and cash equivalents included in "Prepaid expenses and other current assets, net" 20 20 Total cash and cash equivalents and restricted cash and cash equivalents as shown in the Unaudited Consolidated Statements of Cash Flows $ 6,383 $ 6,332

BASIS OF PRESENTATION (Details)

BASIS OF PRESENTATION (Details) - USD ($) $ in Millions	1 Months Ended
	Apr. 30, 2020	Jan. 01, 2020
Organization, Consolidation And Presentation Of Financial Statements [Line Items]
Cumulative effect of adoption of accounting standards updates		$ (3)
Retained Earnings
Organization, Consolidation And Presentation Of Financial Statements [Line Items]
Cumulative effect of adoption of accounting standards updates		$ (3)
Subsequent Event
Organization, Consolidation And Presentation Of Financial Statements [Line Items]
Debt issued	$ 4,100

REVENUE - Geographic Informatio

REVENUE - Geographic Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 2,288	$ 2,837
United States
Disaggregation of Revenue [Line Items]
Revenues	285	366
The Netherlands
Disaggregation of Revenue [Line Items]
Revenues	1,677	2,072
Other
Disaggregation of Revenue [Line Items]
Revenues	$ 326	$ 399

REVENUE - Narrative (Details)

REVENUE - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Reduction in revenue for refunds paid or estimated to be payable	$ 63
Loyalty Programs [Member] | Customer Incentive Programs [Member] | Accrued Liabilities [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Contract liabilities, current	76		$ 80
Other customer incentive programs [Member] | Customer Incentive Programs [Member] | Accrued Liabilities [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Contract liabilities, current	$ 22		$ 22
Online accommodation reservation services [Member] | Revenue Benchmark [Member] | Product Concentration Risk [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Concentration risk percentage	85.00%	84.00%
Other sources of online travel reservation services or advertising and other revenues [Member] | Revenue Benchmark [Member] | Product Concentration Risk [Member] | Maximum
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Concentration risk percentage	10.00%	10.00%

REVENUE - Activity of Deferred

REVENUE - Activity of Deferred Revenue for Online Travel Reservation Services (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)
Contract With Customer, Change In Contract Liability, Current [Roll Forward]
Revenues recognized from the beginning deferred revenue balance	$ (150)
Cancellations	(46)
Payments received from travelers, net of amounts estimated to be payable to travel service providers, and other	120
Deferred revenue in deferred merchant bookings [Member] | Deferred Merchant Bookings [Member]
Contract With Customer, Change In Contract Liability, Current [Roll Forward]
Balance, December 31, 2019	220
Balance, March 31, 2020	$ 144

STOCK-BASED EMPLOYEE COMPENSA_3

STOCK-BASED EMPLOYEE COMPENSATION - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 6	$ 74
Performance Shares [Member] | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate grant-date fair values	$ 265
Restricted Stock Units (RSUs) [Member] | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year
Restricted Stock Units (RSUs) [Member] | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Restricted Stock Units and Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate fair value of performance share units and restricted stock units vested during the period	$ 319
Total unrecognized estimated compensation expense, unvested share-based awards	$ 541
Total future compensation cost related to unvested share-based awards, expected period of recognition	2 years 3 months 18 days
Adjustment for change in estimated probable outcome at the end of the performance period [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 73

STOCK-BASED EMPLOYEE COMPENSA_4

STOCK-BASED EMPLOYEE COMPENSATION - Summary of Share-Based Compensation Activity (Details)	3 Months Ended
	Mar. 31, 2020$ / sharesshares
Restricted Stock Units (RSUs) [Member]
Share-Based Awards - Shares
Unvested (in shares)	256,745
Granted (in shares)	152,832
Vested (in shares)	(109,595)
Forfeited (in shares)	(5,971)
Unvested (in shares)	294,011
Share-Based Awards - Weighted Average Grant Date Fair Value
Unvested (in dollars per share) | $ / shares	$ 1,801
Granted (in dollars per share) | $ / shares	1,732
Vested (in dollars per share) | $ / shares	1,808
Forfeited (in dollars per share) | $ / shares	1,805
Unvested (in dollars per share) | $ / shares	$ 1,762
Performance Shares [Member]
Share-Based Awards - Shares
Unvested (in shares)	216,083
Granted (in shares)	0
Vested (in shares)	(80,266)
Performance share units adjustment (in shares)	(58,427)
Forfeited (in shares)	(2,989)
Unvested (in shares)	74,401
Share-Based Awards - Weighted Average Grant Date Fair Value
Unvested (in dollars per share) | $ / shares	$ 1,835
Vested (in dollars per share) | $ / shares	1,737
Performance share units adjustment (in dollars per share) | $ / shares	1,957
Forfeited (in dollars per share) | $ / shares	1,834
Unvested (in dollars per share) | $ / shares	$ 1,841
Performance Shares [Member] | Performance Share Units 2019 Grants [Member] | Shares probably to be issued [Member]
Share-Based Awards - Shares
Unvested (in shares)	45,361
Performance Shares [Member] | Performance Share Units 2019 Grants [Member] | Shares not subject to achieve minimum performance threshold [Member]
Share-Based Awards - Shares
Unvested (in shares)	45,361
Performance Shares [Member] | Performance Share Units 2019 Grants [Member] | Maximum number of shares that could be issued [Member]
Share-Based Awards - Shares
Unvested (in shares)	117,558
Performance Shares [Member] | Performance Share Units 2018 Grants [Member] | Shares probably to be issued [Member]
Share-Based Awards - Shares
Unvested (in shares)	29,040
Performance Shares [Member] | Performance Share Units 2018 Grants [Member] | Shares not subject to achieve minimum performance threshold [Member]
Share-Based Awards - Shares
Unvested (in shares)	28,647
Performance Shares [Member] | Performance Share Units 2018 Grants [Member] | Maximum number of shares that could be issued [Member]
Share-Based Awards - Shares
Unvested (in shares)	79,914

STOCK-BASED EMPLOYEE COMPENSA_5

STOCK-BASED EMPLOYEE COMPENSATION - Stock Options (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Weighted-average Remaining Contractual Term
Stock option term	10 years
Stock Options
Number of Shares
Balance (in shares)	15,122
Exercised (in shares)	(100)
Balance (in shares)	15,022	15,122
Vested and exercisable (in shares)	15,022
Weighted-average Exercise Price
Balance (in dollars per share)	$ 484
Exercised (in dollars per share)	334
Balance (in dollars per share)	485	$ 484
Vested and exercisable (in dollars per share)	$ 485
Aggregate Intrinsic Value
Balance	$ 24
Balance	13	$ 24
Vested and exercisable	$ 13
Weighted-average Remaining Contractual Term
Balance	2 years 4 months 24 days	2 years 7 months 6 days
Vested and exercisable	2 years 4 months 24 days

NET INCOME PER SHARE (Details)

NET INCOME PER SHARE (Details) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Weighted-average number of basic common shares outstanding (in shares)	41,093,000	45,007,000
Weighted-average dilutive stock options, restricted stock units and performance share units (in shares)	0	229,000
Assumed conversion of Convertible Senior Notes (in shares)	0	200,000
Weighted-average number of diluted common and common equivalent shares outstanding (in shares)	41,093,000	45,436,000
Anti-dilutive potential common shares (in shares)	259,000

INVESTMENTS - Summary of Invest

INVESTMENTS - Summary of Investments by Major Security Type (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Equity security investments in private companies:
Cost		$ 501
Short-term investments:
Carrying Value	$ 826	998
Long-term investments:
Carrying Value	2,056	4,477
Trip.com Group convertible debt securities | Trip.com Group
Debt securities:
Cost	775
Short-term investments
Short-term investments:
Cost	945	998
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(119)	(1)
Carrying Value	826	998
Short-term investments | International government securities
Debt securities:
Cost		109
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Carrying Value		109
Short-term investments | U.S. government securities
Debt securities:
Cost		138
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Carrying Value		138
Short-term investments | Corporate debt securities
Debt securities:
Cost	164	751
Gross Unrealized Gains	0	1
Gross Unrealized Losses	0	(1)
Carrying Value	164	751
Short-term investments | Trip.com Group convertible debt securities | Trip.com Group
Debt securities:
Cost	250
Gross Unrealized Gains	0
Gross Unrealized Losses	(2)
Carrying Value	248
Short-term investments | Equity securities | Trip.com Group
Equity securities:
Cost	531
Gross Unrealized Gains	0
Gross Unrealized Losses	(117)
Carrying Value	414
Long-term investments
Long-term investments:
Cost	1,737	3,810
Gross Unrealized Gains	522	686
Gross Unrealized Losses	(203)	(19)
Carrying Value	2,056	4,477
Long-term investments | Trip.com Group
Equity securities:
Cost		655
Carrying Value		726
Long-term investments | International government securities
Debt securities:
Cost		68
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Carrying Value		68
Long-term investments | U.S. government securities
Debt securities:
Cost		136
Gross Unrealized Gains		0
Gross Unrealized Losses		(1)
Carrying Value		135
Long-term investments | Corporate debt securities
Debt securities:
Cost		963
Gross Unrealized Gains		2
Gross Unrealized Losses		(2)
Carrying Value		963
Long-term investments | Trip.com Group convertible debt securities | Trip.com Group
Debt securities:
Cost	525	775
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(77)	(8)
Carrying Value	448	767
Long-term investments | Debt securities
Debt securities:
Cost	250	250
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(20)	0
Carrying Value	230	250
Long-term investments | Investment in private company equity securities
Equity security investments in private companies:
Cost	501	501
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(100)	0
Carrying Value	401	501
Long-term investments | Equity securities
Equity securities:
Cost	461	1,117
Gross Unrealized Gains	522	684
Gross Unrealized Losses	(6)	(8)
Carrying Value	$ 977	$ 1,793

INVESTMENTS - Narrative (Detail

INVESTMENTS - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	May 07, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Weighted average life of all fixed income investments, excluding the Company's investment in Ctrip convertible debt securities		9 months 18 days
Net (losses) gains on marketable equity securities		$ (307)	$ 451
Cost of investment				$ 501
Corporate debt securities
Schedule of Investments [Line Items]
Impairment of debt securities		3
Corporate debt securities | Subsequent Event
Schedule of Investments [Line Items]
Proceeds from the maturity of debt securities	$ 164
Trip.com Group
Schedule of Investments [Line Items]
Cost basis of securities sold		124
Proceeds from sale of securities		94
Loss on sale of securities		40
Unrealized loss on securities held		178
Net (losses) gains on marketable equity securities			360
Trip.com Group | Subsequent Event
Schedule of Investments [Line Items]
Cost basis of securities sold	531
Proceeds from sale of securities	$ 431
Trip.com Group | Trip.com Group convertible debt securities
Schedule of Investments [Line Items]
Cost of Trip.com Group convertible notes		775
Meituan-Dianping [Member]
Schedule of Investments [Line Items]
Fair value of equity securities		972		1,100
Net (losses) gains on marketable equity securities		(81)	$ 91
Payments to acquire investments					$ 450
Long-term Investments | Corporate debt securities
Schedule of Investments [Line Items]
Cost of Trip.com Group convertible notes				963
Carrying Value				963
Total unrealized losses included in other comprehensive income				2
Long-term Investments | Investment in private company equity securities
Schedule of Investments [Line Items]
Cost of investment		501		501
Equity Securities without Readily Determinable Fair Value, Impairment Loss, Cumulative Amount		100		0
Investment in equity securities without readily determinable FV		401		501
Long-term Investments | Redeemable Convertible Preferred Stock [Member]
Schedule of Investments [Line Items]
Cost of Trip.com Group convertible notes		250
Carrying Value		230		250
Long-term Investments | Trip.com Group
Schedule of Investments [Line Items]
Cost of investment in equity securities				655
Fair value of equity securities				726
Long-term Investments | Trip.com Group | Trip.com Group convertible debt securities
Schedule of Investments [Line Items]
Cost of Trip.com Group convertible notes		525		775
Carrying Value		448		767
Total unrealized losses included in other comprehensive income		77		8
Long-term Investments | Trip.com Group 1.25% Notes due 2022 | Trip.com Group convertible debt securities
Schedule of Investments [Line Items]
Cost of Trip.com Group convertible notes						$ 25
Long-term Investments | Didi Chuxing | Investment in private company equity securities
Schedule of Investments [Line Items]
Cost of investment				500
Investment in equity securities without readily determinable FV		400
Long-term Investments | Grab | Redeemable Convertible Preferred Stock [Member]
Schedule of Investments [Line Items]
Carrying Value		180		200
Total unrealized losses included in other comprehensive income		20
Short-term Investments | Corporate debt securities
Schedule of Investments [Line Items]
Cost of Trip.com Group convertible notes		164		751
Carrying Value		164		751
Total unrealized losses included in other comprehensive income		0		$ 1
Short-term Investments | Trip.com Group convertible debt securities
Schedule of Investments [Line Items]
Investments in debt securities reclassified from long-term to short term		103
Short-term Investments | Trip.com Group
Schedule of Investments [Line Items]
Investments in ADS reclassified from long-term to short term		414
Short-term Investments | Trip.com Group | Trip.com Group convertible debt securities
Schedule of Investments [Line Items]
Cost of Trip.com Group convertible notes		250
Carrying Value		248
Total unrealized losses included in other comprehensive income		2
Short-term Investments | Trip.com Group 1% Note Due 2020 [Member] | Trip.com Group convertible debt securities
Schedule of Investments [Line Items]
Cost of Trip.com Group convertible notes		$ 250

FAIR VALUE MEASUREMENTS - Finan

FAIR VALUE MEASUREMENTS - Financial Assets and Liabilities Carried at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Recurring Basis
ASSETS:
Assets at fair value	$ 8,463	$ 10,751
Recurring Basis | Long-term Investments
ASSETS:
Assets at fair value	230	250
Recurring Basis | Money market funds | Cash Equivalents
ASSETS:
Assets at fair value	5,944	5,734
Recurring Basis | Time deposits and certificates of deposit | Cash Equivalents
ASSETS:
Assets at fair value	26	29
Recurring Basis | International government securities | Short-term Investments
ASSETS:
Assets at fair value		109
Recurring Basis | International government securities | Long-term Investments
ASSETS:
Assets at fair value		68
Recurring Basis | U.S. government securities | Short-term Investments
ASSETS:
Assets at fair value		138
Recurring Basis | U.S. government securities | Long-term Investments
ASSETS:
Assets at fair value		135
Recurring Basis | Corporate debt securities | Short-term Investments
ASSETS:
Assets at fair value	164	751
Recurring Basis | Corporate debt securities | Long-term Investments
ASSETS:
Assets at fair value		963
Recurring Basis | Corporate debt securities | Cash Equivalents
ASSETS:
Assets at fair value		2
Recurring Basis | Equity securities | Long-term Investments
ASSETS:
Assets at fair value	977	1,793
Recurring Basis | Trip.com Group | Trip.com Group convertible debt securities | Short-term Investments
ASSETS:
Assets at fair value	248
Recurring Basis | Trip.com Group | Trip.com Group convertible debt securities | Long-term Investments
ASSETS:
Assets at fair value	448	767
Recurring Basis | Trip.com Group | Equity securities | Short-term Investments
ASSETS:
Assets at fair value	414
Recurring Basis | Not Designated as Hedging Instrument | Foreign Currency Contracts
ASSETS:
Assets at fair value	12	12
LIABILITIES:
Liabilities at fair value	21	5
Nonrecurring Basis
ASSETS:
Assets at fair value	1,945
Nonrecurring Basis | Equity securities | Long-term Investments
ASSETS:
Assets at fair value	400
Nonrecurring Basis | Goodwill
ASSETS:
Assets at fair value	1,545
Level 1 | Recurring Basis
ASSETS:
Assets at fair value	7,361	7,556
Level 1 | Recurring Basis | Long-term Investments
ASSETS:
Assets at fair value	0	0
Level 1 | Recurring Basis | Money market funds | Cash Equivalents
ASSETS:
Assets at fair value	5,944	5,734
Level 1 | Recurring Basis | Time deposits and certificates of deposit | Cash Equivalents
ASSETS:
Assets at fair value	26	29
Level 1 | Recurring Basis | International government securities | Short-term Investments
ASSETS:
Assets at fair value		0
Level 1 | Recurring Basis | International government securities | Long-term Investments
ASSETS:
Assets at fair value		0
Level 1 | Recurring Basis | U.S. government securities | Short-term Investments
ASSETS:
Assets at fair value		0
Level 1 | Recurring Basis | U.S. government securities | Long-term Investments
ASSETS:
Assets at fair value		0
Level 1 | Recurring Basis | Corporate debt securities | Short-term Investments
ASSETS:
Assets at fair value	0	0
Level 1 | Recurring Basis | Corporate debt securities | Long-term Investments
ASSETS:
Assets at fair value		0
Level 1 | Recurring Basis | Corporate debt securities | Cash Equivalents
ASSETS:
Assets at fair value		0
Level 1 | Recurring Basis | Equity securities | Long-term Investments
ASSETS:
Assets at fair value	977	1,793
Level 1 | Recurring Basis | Trip.com Group | Trip.com Group convertible debt securities | Short-term Investments
ASSETS:
Assets at fair value	0
Level 1 | Recurring Basis | Trip.com Group | Trip.com Group convertible debt securities | Long-term Investments
ASSETS:
Assets at fair value	0	0
Level 1 | Recurring Basis | Trip.com Group | Equity securities | Short-term Investments
ASSETS:
Assets at fair value	414
Level 1 | Recurring Basis | Not Designated as Hedging Instrument | Foreign Currency Contracts
ASSETS:
Assets at fair value	0	0
LIABILITIES:
Liabilities at fair value	0	0
Level 1 | Nonrecurring Basis
ASSETS:
Assets at fair value	0
Level 1 | Nonrecurring Basis | Equity securities | Long-term Investments
ASSETS:
Assets at fair value	0
Level 1 | Nonrecurring Basis | Goodwill
ASSETS:
Assets at fair value	0
Level 2 | Recurring Basis
ASSETS:
Assets at fair value	872	2,945
Level 2 | Recurring Basis | Long-term Investments
ASSETS:
Assets at fair value	0	0
Level 2 | Recurring Basis | Money market funds | Cash Equivalents
ASSETS:
Assets at fair value	0	0
Level 2 | Recurring Basis | Time deposits and certificates of deposit | Cash Equivalents
ASSETS:
Assets at fair value	0	0
Level 2 | Recurring Basis | International government securities | Short-term Investments
ASSETS:
Assets at fair value		109
Level 2 | Recurring Basis | International government securities | Long-term Investments
ASSETS:
Assets at fair value		68
Level 2 | Recurring Basis | U.S. government securities | Short-term Investments
ASSETS:
Assets at fair value		138
Level 2 | Recurring Basis | U.S. government securities | Long-term Investments
ASSETS:
Assets at fair value		135
Level 2 | Recurring Basis | Corporate debt securities | Short-term Investments
ASSETS:
Assets at fair value	164	751
Level 2 | Recurring Basis | Corporate debt securities | Long-term Investments
ASSETS:
Assets at fair value		963
Level 2 | Recurring Basis | Corporate debt securities | Cash Equivalents
ASSETS:
Assets at fair value		2
Level 2 | Recurring Basis | Equity securities | Long-term Investments
ASSETS:
Assets at fair value	0	0
Level 2 | Recurring Basis | Trip.com Group | Trip.com Group convertible debt securities | Short-term Investments
ASSETS:
Assets at fair value	248
Level 2 | Recurring Basis | Trip.com Group | Trip.com Group convertible debt securities | Long-term Investments
ASSETS:
Assets at fair value	448	767
Level 2 | Recurring Basis | Trip.com Group | Equity securities | Short-term Investments
ASSETS:
Assets at fair value	0
Level 2 | Recurring Basis | Not Designated as Hedging Instrument | Foreign Currency Contracts
ASSETS:
Assets at fair value	12	12
LIABILITIES:
Liabilities at fair value	21	5
Level 2 | Nonrecurring Basis
ASSETS:
Assets at fair value	0
Level 2 | Nonrecurring Basis | Equity securities | Long-term Investments
ASSETS:
Assets at fair value	0
Level 2 | Nonrecurring Basis | Goodwill
ASSETS:
Assets at fair value	0
Level 3 | Recurring Basis
ASSETS:
Assets at fair value	230	250
Level 3 | Recurring Basis | Long-term Investments
ASSETS:
Assets at fair value	230	250
Level 3 | Recurring Basis | Money market funds | Cash Equivalents
ASSETS:
Assets at fair value	0	0
Level 3 | Recurring Basis | Time deposits and certificates of deposit | Cash Equivalents
ASSETS:
Assets at fair value	0	0
Level 3 | Recurring Basis | International government securities | Short-term Investments
ASSETS:
Assets at fair value		0
Level 3 | Recurring Basis | International government securities | Long-term Investments
ASSETS:
Assets at fair value		0
Level 3 | Recurring Basis | U.S. government securities | Short-term Investments
ASSETS:
Assets at fair value		0
Level 3 | Recurring Basis | U.S. government securities | Long-term Investments
ASSETS:
Assets at fair value		0
Level 3 | Recurring Basis | Corporate debt securities | Short-term Investments
ASSETS:
Assets at fair value	0	0
Level 3 | Recurring Basis | Corporate debt securities | Long-term Investments
ASSETS:
Assets at fair value		0
Level 3 | Recurring Basis | Corporate debt securities | Cash Equivalents
ASSETS:
Assets at fair value		0
Level 3 | Recurring Basis | Equity securities | Long-term Investments
ASSETS:
Assets at fair value	0	0
Level 3 | Recurring Basis | Trip.com Group | Trip.com Group convertible debt securities | Short-term Investments
ASSETS:
Assets at fair value	0
Level 3 | Recurring Basis | Trip.com Group | Trip.com Group convertible debt securities | Long-term Investments
ASSETS:
Assets at fair value	0	0
Level 3 | Recurring Basis | Trip.com Group | Equity securities | Short-term Investments
ASSETS:
Assets at fair value	0
Level 3 | Recurring Basis | Not Designated as Hedging Instrument | Foreign Currency Contracts
ASSETS:
Assets at fair value	0	0
LIABILITIES:
Liabilities at fair value	0	$ 0
Level 3 | Nonrecurring Basis
ASSETS:
Assets at fair value	1,945
Level 3 | Nonrecurring Basis | Equity securities | Long-term Investments
ASSETS:
Assets at fair value	400
Level 3 | Nonrecurring Basis | Goodwill
ASSETS:
Assets at fair value	$ 1,545

FAIR VALUE MEASUREMENTS - Rollf

FAIR VALUE MEASUREMENTS - Rollforward of Level 3 Fair Value Measurements (Details) - Recurring Basis - Level 3 $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)
Debt Securities, Available For Sale, Change In Fair Value [Roll Forward]
Balance, December 31, 2019	$ 250
Total unrealized losses included in other comprehensive income	(20)
Balance, March 31, 2020	$ 230

FAIR VALUE MEASUREMENTS - Narra

FAIR VALUE MEASUREMENTS - Narrative (Details) $ in Millions	Mar. 31, 2020USD ($)Years	Dec. 31, 2016USD ($)
Didi Chuxing | Long-term Investments | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in equity securities without readily determinable FV	$ 400
Grab | Long-term Investments | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	$ 180
Trip.com Group 1.25% Notes due 2022 | Long-term Investments | Trip.com Group convertible debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cost of Trip.com Group convertible notes		$ 25
Weighted Average Cost of Capital | Grab and Didi Chuxing [Member] | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement, inputs (percentages)	12.00%
Weighted Average Cost of Capital | Grab and Didi Chuxing [Member] | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement, inputs (percentages)	14.00%
EBITDA Multiple | Grab and Didi Chuxing [Member] | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement, inputs (number)	13
EBITDA Multiple | Grab and Didi Chuxing [Member] | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement, inputs (number)	15
Volatility | Grab and Didi Chuxing [Member] | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement, inputs (percentages)	60.00%
Volatility | Grab and Didi Chuxing [Member] | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement, inputs (percentages)	70.00%
Expected Term | Grab and Didi Chuxing [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement, inputs (number) | Years	4
Valuation, Market Approach [Member] | Grab
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement inputs, valuation approach allocation	25.00%
Valuation, Income Approach [Member] | Grab
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement inputs, valuation approach allocation	75.00%

FAIR VALUE MEASUREMENTS - Notio

FAIR VALUE MEASUREMENTS - Notional Amount of Foreign Currency Exchange Derivatives (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Recurring Basis
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Assets at fair value	$ 8,463	$ 10,751
Recurring Basis | Level 2
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Assets at fair value	872	2,945
Recurring Basis | Not Designated as Hedging Instrument | Foreign Currency Contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Assets at fair value	12	12
Liabilities at fair value	21	5
Recurring Basis | Not Designated as Hedging Instrument | Level 2 | Foreign Currency Contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Assets at fair value	12	12
Liabilities at fair value	21	5
Foreign currency purchases | Not Designated as Hedging Instrument | Foreign Currency Contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	1,441	1,770
Foreign currency sales | Not Designated as Hedging Instrument | Foreign Currency Contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	$ 950	$ 901

FAIR VALUE MEASUREMENTS - Effec

FAIR VALUE MEASUREMENTS - Effect of Foreign Currency Exchange Derivatives (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Losses on foreign currency exchange derivatives	$ 23	$ 13

ACCOUNTS RECEIVABLE AND OTHER_3

ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Prepaid expense, allowance for credit loss	$ 54		$ 6
Contract With Customer, Reduction To Revenue, Cancellation Refunds	63
Accounts receivable, net (Allowance for credit losses of $245 and $49, respectively)	667
Accounts Receivable, after Allowance for Credit Loss [Abstract]
Accounts Receivable, Allowance for Credit Loss	49	$ 51
Provision for expected credit losses and chargebacks	199	17
Accounts Receivable, Allowance for Credit Loss, Writeoff	(1)	(18)
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	(2)	(1)
Accounts Receivable, Allowance for Credit Loss	245	$ 49
Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net (Allowance for credit losses of $245 and $49, respectively)	740		1,200
Marketing Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net (Allowance for credit losses of $245 and $49, respectively)	61		110
COVID-19 [Member]
Accounts Receivable, after Allowance for Credit Loss [Abstract]
Provision for expected credit losses and chargebacks	183
Prepaid expenses and other current assets, net
Accounts, Notes, Loans and Financing Receivable [Line Items]
Prepaid expense, allowance for credit loss	5		6
Prepaid Expense	104		232
Other assets, net
Accounts, Notes, Loans and Financing Receivable [Line Items]
Prepaid expense, allowance for credit loss	49		$ 0
Prepaid Expense	126
Contract With Customer, Reduction To Revenue, Cancellation Refunds [Member]
Accounts Receivable, after Allowance for Credit Loss [Abstract]
Provision for expected credit losses and chargebacks	$ 48

INTANGIBLE ASSETS AND GOODWIL_2

INTANGIBLE ASSETS AND GOODWILL - Changes in Goodwill (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 2,913
Goodwill, Impairment Loss	(489)	$ 0
Goodwill, Foreign Currency Translation Gain (Loss)	(33)
Goodwill	$ 2,391

INTANGIBLE ASSETS AND GOODWIL_3

INTANGIBLE ASSETS AND GOODWILL (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Finite-lived intangible assets
Goodwill, Impaired, Accumulated Impairment Loss	$ 1,400		$ 941
Gross Carrying Amount	3,095		3,123
Accumulated Amortization	(1,198)		(1,169)
Net Carrying Amount	1,897		1,954
Amortization expense	43	$ 45
Impairment of goodwill	489	$ 0
Goodwill	2,391		2,913
Supply and distribution agreements
Finite-lived intangible assets
Gross Carrying Amount	1,083		1,100
Accumulated Amortization	(478)		(472)
Net Carrying Amount	605		628
Technology
Finite-lived intangible assets
Gross Carrying Amount	169		170
Accumulated Amortization	(131)		(129)
Net Carrying Amount	38		41
Internet domain names
Finite-lived intangible assets
Gross Carrying Amount	39		40
Accumulated Amortization	(32)		(32)
Net Carrying Amount	7		8
Trade Names
Finite-lived intangible assets
Gross Carrying Amount	1,802		1,811
Accumulated Amortization	(555)		(534)
Net Carrying Amount	1,247		1,277
Other Intangible Assets
Finite-lived intangible assets
Gross Carrying Amount	2		2
Accumulated Amortization	(2)		(2)
Net Carrying Amount	$ 0		$ 0
Minimum | Supply and distribution agreements
Finite-lived intangible assets
Amortization Period	3 years
Minimum | Technology
Finite-lived intangible assets
Amortization Period	2 years
Minimum | Internet domain names
Finite-lived intangible assets
Amortization Period	5 years
Minimum | Trade Names
Finite-lived intangible assets
Amortization Period	4 years
Minimum | Other Intangible Assets
Finite-lived intangible assets
Amortization Period	0 years
Maximum | Supply and distribution agreements
Finite-lived intangible assets
Amortization Period	20 years
Maximum | Technology
Finite-lived intangible assets
Amortization Period	7 years
Maximum | Internet domain names
Finite-lived intangible assets
Amortization Period	20 years
Maximum | Trade Names
Finite-lived intangible assets
Amortization Period	20 years
Maximum | Other Intangible Assets
Finite-lived intangible assets
Amortization Period	15 years
OpenTable And KAYAK [Member]
Finite-lived intangible assets
Impairment of goodwill	$ 489
Goodwill	1,500
OpenTable And KAYAK [Member] | Minimum
Finite-lived intangible assets
Reporting Unit, Estimated Impact On Fair Value Assessment	(410)
OpenTable And KAYAK [Member] | Maximum
Finite-lived intangible assets
Reporting Unit, Estimated Impact On Fair Value Assessment	$ 230

DEBT (Revolving Credit Facility

DEBT (Revolving Credit Facility) (Details) - USD ($)	1 Months Ended		3 Months Ended
	Aug. 31, 2019	Jun. 30, 2015	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2019
Line of Credit Facility [Line Items]
Long-term Debt			$ 7,553,000,000			$ 7,640,000,000
Letters of credit issued			5,000,000			5,000,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility, maximum borrowing capacity	$ 2,000,000,000	$ 2,000,000,000
Line of credit facility, term	5 years	5 years
Line of credit, current			0			$ 0
Proceeds from revolving credit facility and short-term borrowings					$ 250,000,000
Weighted average interest rate					3.50%
Repayments of Lines of Credit				$ 250,000,000
Revolving Credit Facility | Minimum
Line of Credit Facility [Line Items]
Commitment fee rate	0.07%
Revolving Credit Facility | Minimum | Rate 2C
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.00%
Revolving Credit Facility | Maximum
Line of Credit Facility [Line Items]
Commitment fee rate	0.20%
Revolving Credit Facility | Maximum | Rate 2C
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.50%
Revolving Credit Facility | London Interbank Offered Rate (LIBOR) | Minimum | Rate 1
Line of Credit Facility [Line Items]
Debt Instrument, Reference Rate	0.00%
Basis spread on variable rate	0.875%
Revolving Credit Facility | London Interbank Offered Rate (LIBOR) | Maximum | Rate 1
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.50%
Revolving Credit Facility | Federal Funds Purchased | Rate 2B
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.50%
Revolving Credit Facility | One Month LIBOR | Rate 2C
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.00%
Revolving Credit Facility | One Month LIBOR | Minimum | Rate 2C
Line of Credit Facility [Line Items]
Debt Instrument, Reference Rate	0.00%
Letter of Credit
Line of Credit Facility [Line Items]
Revolving credit facility, maximum borrowing capacity	$ 80,000,000
Swingline Loans
Line of Credit Facility [Line Items]
Revolving credit facility, maximum borrowing capacity	$ 100,000,000
0.35% Convertible Senior Notes due June 2020
Line of Credit Facility [Line Items]
Amortization of Debt Discount (Premium)			$ 1,000,000		$ 1,000,000

DEBT (Outstanding Debt) (Detail

DEBT (Outstanding Debt) (Details)	1 Months Ended			3 Months Ended		12 Months Ended
	Apr. 30, 2020USD ($)Days$ / shares	Aug. 31, 2014USD ($)Days$ / shares	May 31, 2013USD ($)Days$ / shares	Mar. 31, 2020USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Mar. 31, 2020EUR (€)	Dec. 31, 2019USD ($)	Dec. 31, 2019EUR (€)	Aug. 31, 2017	Mar. 31, 2017	May 31, 2016	Nov. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Jun. 30, 2013USD ($)
Debt Instrument
Convertible debt				$ 4,000,000					$ 0
Outstanding Principal Amount, Long-Term Debt				7,615,000,000					7,711,000,000
Unamortized Debt Discount and Debt Issuance Cost				(62,000,000)					(71,000,000)
Long-term Debt				$ 7,553,000,000					$ 7,640,000,000
0.35% Convertible Senior Notes due June 2020
Description of Senior Notes
Aggregate principal amount			$ 1,000,000,000
Interest rate on long-term debt			0.35%	0.35%				0.35%	0.35%	0.35%
Debt financing costs paid							$ 1,000,000
Convertible debt conversion price (in dollars per share) | $ / shares			$ 1,315.10
Ratio of closing share price to conversion price as a condition for conversion of the convertible notes, minimum			150.00%
if-converted value over the aggregate principal amount				$ 92,000,000
Unamortized debt discount			$ 20,000,000
Effective interest rate at debt origination or modification			3.13%
Debt discount related to convertible notes, net of tax																	$ 92,000,000
Debt discount related to convertible notes, before tax																	$ 154,000,000
Amortization of debt discount included in interest expense				1,000,000	$ 1,000,000
0.9% Convertible Senior Notes due September 2021
Debt Instrument
Outstanding Principal Amount, Long-Term Debt				1,000,000,000					$ 1,000,000,000
Unamortized Debt Discount and Debt Issuance Cost				(33,000,000)					(39,000,000)
Long-term Debt				$ 967,000,000					$ 961,000,000
Description of Senior Notes
Aggregate principal amount		$ 1,000,000,000
Interest rate on long-term debt		0.90%		0.90%				0.90%	0.90%	0.90%
Debt financing costs paid						$ 11,000,000
Convertible debt conversion price (in dollars per share) | $ / shares		$ 2,055.50
Ratio of closing share price to conversion price as a condition for conversion of the convertible notes, minimum		150.00%
Effective interest rate at debt origination or modification		3.18%
Debt discount related to convertible notes, net of tax						83,000,000
Debt discount related to convertible notes, before tax						$ 143,000,000
0.8% (€1 Billion) Senior Notes due March 2022
Debt Instrument
Outstanding Principal Amount, Long-Term Debt				$ 1,097,000,000					$ 1,123,000,000
Unamortized Debt Discount and Debt Issuance Cost				(3,000,000)					(3,000,000)
Long-term Debt				$ 1,094,000,000					$ 1,120,000,000
Description of Senior Notes
Aggregate principal amount | €								€ 1,000,000,000		€ 1,000,000,000
Interest rate on long-term debt				0.80%				0.80%	0.80%	0.80%
Effective interest rate at debt origination or modification												0.84%
2.15% (€750 Million) Senior Notes due November 2022
Debt Instrument
Outstanding Principal Amount, Long-Term Debt				$ 824,000,000					$ 842,000,000
Unamortized Debt Discount and Debt Issuance Cost				(2,000,000)					(3,000,000)
Long-term Debt				$ 822,000,000					$ 839,000,000
Description of Senior Notes
Aggregate principal amount | €								€ 750,000,000		€ 750,000,000
Interest rate on long-term debt				2.15%				2.15%	2.15%	2.15%
Effective interest rate at debt origination or modification														2.20%
2.75% Senior Notes due March 2023
Debt Instrument
Outstanding Principal Amount, Long-Term Debt				$ 500,000,000					$ 500,000,000
Unamortized Debt Discount and Debt Issuance Cost				(2,000,000)					(2,000,000)
Long-term Debt				$ 498,000,000					$ 498,000,000
Description of Senior Notes
Interest rate on long-term debt				2.75%				2.75%	2.75%	2.75%
Effective interest rate at debt origination or modification											2.78%
2.375% (€1 Billion) Senior Notes due September 2024
Debt Instrument
Outstanding Principal Amount, Long-Term Debt				$ 1,097,000,000					$ 1,123,000,000
Unamortized Debt Discount and Debt Issuance Cost				(8,000,000)					(9,000,000)
Long-term Debt				$ 1,089,000,000					$ 1,114,000,000
Description of Senior Notes
Aggregate principal amount | €								€ 1,000,000,000		€ 1,000,000,000
Interest rate on long-term debt				2.375%				2.375%	2.375%	2.375%
Effective interest rate at debt origination or modification																2.48%
3.65% Senior Notes Due March 2025 [Member]
Debt Instrument
Outstanding Principal Amount, Long-Term Debt				$ 500,000,000					$ 500,000,000
Unamortized Debt Discount and Debt Issuance Cost				(2,000,000)					(2,000,000)
Long-term Debt				$ 498,000,000					$ 498,000,000
Description of Senior Notes
Interest rate on long-term debt				3.65%				3.65%	3.65%	3.65%
Effective interest rate at debt origination or modification															3.68%
3.6% Senior Notes due June 2026
Debt Instrument
Outstanding Principal Amount, Long-Term Debt				$ 1,000,000,000					$ 1,000,000,000
Unamortized Debt Discount and Debt Issuance Cost				(5,000,000)					(5,000,000)
Long-term Debt				$ 995,000,000					$ 995,000,000
Description of Senior Notes
Interest rate on long-term debt				3.60%				3.60%	3.60%	3.60%
Effective interest rate at debt origination or modification													3.62%
1.8% (€1 Billion) Senior Notes due March 2027
Debt Instrument
Outstanding Principal Amount, Long-Term Debt				$ 1,097,000,000					$ 1,123,000,000
Unamortized Debt Discount and Debt Issuance Cost				(4,000,000)					(5,000,000)
Long-term Debt				$ 1,093,000,000					$ 1,118,000,000
Description of Senior Notes
Aggregate principal amount | €								€ 1,000,000,000		€ 1,000,000,000
Interest rate on long-term debt				1.80%				1.80%	1.80%	1.80%
Effective interest rate at debt origination or modification															1.80%
3.55% Senior Notes due March 2028
Debt Instrument
Outstanding Principal Amount, Long-Term Debt				$ 500,000,000					$ 500,000,000
Unamortized Debt Discount and Debt Issuance Cost				(3,000,000)					(3,000,000)
Long-term Debt				$ 497,000,000					$ 497,000,000
Description of Senior Notes
Interest rate on long-term debt				3.55%				3.55%	3.55%	3.55%
Effective interest rate at debt origination or modification											3.56%
Convertible Debt
Description of Senior Notes
Interest expense related to debt				$ 15,000,000	15,000,000
Amortization of debt discount included in interest expense				12,000,000	12,000,000
Coupon Interest expense				$ 3,000,000	$ 3,000,000
Debt, weighted average interest rate				3.20%	3.20%
Other Long-term Debt
Debt Instrument
Long-term Debt				$ 6,600,000,000					$ 6,700,000,000
Description of Senior Notes
Interest expense related to debt				42,000,000	$ 42,000,000
Coupon Interest expense				40,000,000	$ 40,000,000
Minimum | 0.35% Convertible Senior Notes due June 2020
Description of Senior Notes
Minimum and Maximum consecutive days the closing sales price of common stock must exceed a specified percentage of conversion price to trigger conversion feature of note (in days) | Days			20
Additional payment to debt holder, settled In shares, aggregate value			$ 0
Minimum | 0.9% Convertible Senior Notes due September 2021
Description of Senior Notes
Minimum and Maximum consecutive days the closing sales price of common stock must exceed a specified percentage of conversion price to trigger conversion feature of note (in days) | Days		20
Additional payment to debt holder, settled In shares, aggregate value		$ 0
Maximum | 0.35% Convertible Senior Notes due June 2020
Description of Senior Notes
Minimum and Maximum consecutive days the closing sales price of common stock must exceed a specified percentage of conversion price to trigger conversion feature of note (in days) | Days			30
Additional payment to debt holder, settled In shares, aggregate value			$ 397,000,000
Maximum | 0.9% Convertible Senior Notes due September 2021
Description of Senior Notes
Minimum and Maximum consecutive days the closing sales price of common stock must exceed a specified percentage of conversion price to trigger conversion feature of note (in days) | Days		30
Additional payment to debt holder, settled In shares, aggregate value		$ 375,000,000
Level 2
Description of Senior Notes
Estimated market value of outstanding debt				8,700,000,000					9,800,000,000
Designated as Hedging Instrument | Minimum | Euro-Denominated Debt
Description of Senior Notes
Notional amount of nonderivative instruments				2,100,000,000
Designated as Hedging Instrument | Maximum | Euro-Denominated Debt
Description of Senior Notes
Notional amount of nonderivative instruments				3,200,000,000
Short-term Debt [Member] | 0.35% Convertible Senior Notes due June 2020
Debt Instrument
Outstanding Principal Amount, Short-Term Debt				1,000,000,000					1,000,000,000
Unamortized Debt Discount and Debt Issuance Cost				(5,000,000)					(12,000,000)
Carrying Value, Short-term debt				995,000,000					988,000,000
Recurring Basis
Debt Instrument
Debt Securities, Available-for-sale, Amortized Cost				8,463,000,000					10,751,000,000
Recurring Basis | Level 3
Debt Instrument
Debt Securities, Available-for-sale, Amortized Cost				230,000,000					250,000,000
Description of Senior Notes
Carrying Value				230,000,000					250,000,000
Debt Securities, Available-for-sale, Unrealized Loss				20,000,000
Recurring Basis | Level 2
Debt Instrument
Debt Securities, Available-for-sale, Amortized Cost				872,000,000					2,945,000,000
Long-term Investments | Recurring Basis
Debt Instrument
Debt Securities, Available-for-sale, Amortized Cost				230,000,000					250,000,000
Long-term Investments | Recurring Basis | Level 3
Debt Instrument
Debt Securities, Available-for-sale, Amortized Cost				230,000,000					250,000,000
Long-term Investments | Recurring Basis | Level 2
Debt Instrument
Debt Securities, Available-for-sale, Amortized Cost				0					0
Redeemable Convertible Preferred Stock [Member] | Long-term Investments
Description of Senior Notes
Carrying Value				$ 230,000,000					$ 250,000,000
Subsequent Event | 3.65% Senior Notes due March 2025
Debt Instrument
Outstanding Principal Amount, Long-Term Debt	$ 1,000,000,000
Description of Senior Notes
Interest rate on long-term debt	4.10%
Subsequent Event | 0.75% Senior Convertible Notes Due May 2025 [Member] [Member]
Description of Senior Notes
Aggregate principal amount	$ 863,000,000
Interest rate on long-term debt	0.75%
Convertible debt conversion price (in dollars per share) | $ / shares	$ 1,886.44
Ratio of closing share price to conversion price as a condition for conversion of the convertible notes, minimum	130.00%
Subsequent Event | 4.5% Senior Notes Due April 2027 [Member]
Debt Instrument
Outstanding Principal Amount, Long-Term Debt	$ 750,000,000
Description of Senior Notes
Interest rate on long-term debt	4.50%
Subsequent Event | 4.625% Senior Notes Due April 2030 [Member]
Debt Instrument
Outstanding Principal Amount, Long-Term Debt	$ 1,500,000,000
Description of Senior Notes
Interest rate on long-term debt	4.625%
Subsequent Event | Minimum | 0.75% Senior Convertible Notes Due May 2025 [Member] [Member]
Description of Senior Notes
Minimum and Maximum consecutive days the closing sales price of common stock must exceed a specified percentage of conversion price to trigger conversion feature of note (in days) | Days	20
Additional payment to debt holder, settled In shares, aggregate value	$ 0
Subsequent Event | Maximum | 0.75% Senior Convertible Notes Due May 2025 [Member] [Member]
Description of Senior Notes
Minimum and Maximum consecutive days the closing sales price of common stock must exceed a specified percentage of conversion price to trigger conversion feature of note (in days) | Days	30
Additional payment to debt holder, settled In shares, aggregate value	$ 273,000,000

TREASURY STOCK (Details)

TREASURY STOCK (Details) - USD ($)	1 Months Ended	3 Months Ended
	Dec. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Jun. 30, 2019
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock through authorized stock repurchase programs (in shares)		678,000	1,619,000
Repurchase of common stock through authorized stock repurchase programs		$ 1,251,000,000	$ 2,856,000,000
Repurchase of common stock through general authorization for shares withheld on stock award vesting (in shares)		77,000	71,000
Repurchase of common stock through general authorization for shares withheld on stock award vesting		$ 129,000,000	$ 121,000,000
Treasury stock repurchased but unsettled by period end, amount	$ 40,000,000
Payments related to tax withholding for share-based compensation		$ 119,000,000	$ 111,000,000
Treasury stock, shares (in shares)	21,762,070	22,439,549
2019 Share Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Remaining authorization to repurchase common stock	$ 11,500,000,000	$ 10,400,000,000
Amount of common stock repurchases authorized				$ 15,000,000,000
Common Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock through authorized stock repurchase programs (in shares)		601,000	1,548,000
Repurchase of common stock through authorized stock repurchase programs		$ 1,122,000,000	$ 2,735,000,000

INCOME TAXES (Details)

INCOME TAXES (Details)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Tax Contingency [Line Items]
Effective income tax rate reconciliation, percent	3.10%	21.00%
Statutory federal rate	21.00%
Tax and Customs Administration, Netherlands
Income Tax Contingency [Line Items]
Statutory federal rate	25.00%
Effective income tax rate at innovation box tax rate	7.00%

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	$ 3,831	$ 6,915	$ 5,933	$ 8,785
OCI, before Reclassifications, Net of Tax, Attributable to Parent	(154)	148
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent	3	(1)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(151)	147
Accumulated Foreign Currency Adjustment Attributable To Parent, Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity, before tax	(314)	(189)	(186)	(109)
AOCI tax, attributable to parent	(58)	(52)	(54)	(41)
OCI, before Reclassifications, before Tax, Attributable to Parent	(128)	(80)
Other Comprehensive Income (Loss) before Reclassifications, Tax	4	11
Reclassification from AOCI, Current Period, before Tax, Attributable to Parent	0	0
Reclassification from AOCI, Current Period, Tax	0	0
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent	(128)	(80)
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	4	11
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	(216)	(141)	(139)	(129)
OCI, before Reclassifications, Net of Tax, Attributable to Parent	(77)	(12)
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(77)	(12)
Foreign currency translation adjustments | Net Investment Hedging | Foreign Currency Forward
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	(35)	(35)	(35)	(35)
Stockholders' equity, before tax	(53)	(53)	(53)	(53)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	(342)	(169)	(191)	(316)
Accumulated Net Investment Gain (Loss) Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	(126)	(28)	(52)	(187)
Stockholders' equity, before tax	(97)	53	(7)	(157)
AOCI tax, attributable to parent	29	81	45	30
OCI, before Reclassifications, before Tax, Attributable to Parent	(94)	211
Other Comprehensive Income (Loss) before Reclassifications, Tax	17	(51)
OCI, before Reclassifications, Net of Tax, Attributable to Parent	(77)	160
Reclassification from AOCI, Current Period, before Tax, Attributable to Parent	4	(1)
Reclassification from AOCI, Current Period, Tax	(1)	0
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent	3	(1)
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent	(90)	210
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	16	(51)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(74)	159
Accumulated Foreign Currency Adjustment Attributable To Parent, Net Investment Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity, before tax	60	3	(2)	(73)
AOCI tax, attributable to parent	20	7	$ 5	$ (12)
OCI, before Reclassifications, before Tax, Attributable to Parent	62	76
Other Comprehensive Income (Loss) before Reclassifications, Tax	(15)	(19)
Reclassification from AOCI, Current Period, before Tax, Attributable to Parent	0	0
Reclassification from AOCI, Current Period, Tax	0	0
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent	62	76
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	$ (15)	$ (19)

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details) ₺ in Millions, € in Millions, £ in Millions, $ in Millions

1 Months Ended

3 Months Ended

12 Months Ended

Dec. 31, 2019USD ($)

Dec. 31, 2019EUR (€)

Jan. 31, 2019USD ($)

Jan. 31, 2019EUR (€)

Dec. 31, 2015EUR (€)

Mar. 31, 2020USD ($)

Mar. 31, 2020EUR (€)

Sep. 30, 2016USD ($)

Sep. 30, 2016EUR (€)

Dec. 31, 2019USD ($)

Dec. 31, 2019TRY (₺)

Dec. 31, 2018USD ($)ft²

Dec. 31, 2018EUR (€)ft²

May 07, 2020USD ($)

May 07, 2020EUR (€)

Mar. 31, 2020EUR (€)

Mar. 31, 2020GBP (£)

Booking.com | Headquarters

Commitments and Contingencies

Contractual obligation

$ 112

€ 102

Acquisition of land use rights

$ 48

€ 43

Payment Of Contractual Obligation

193

€ 168

Booking.com | Headquarters | Ground Lease

Commitments and Contingencies

Contractual obligation

78

€ 71

French Tax Audit

Commitments and Contingencies

Assessed taxes including interest and penalties

$ 77

€ 70

€ 356

Payment required to appeal a litigation matter

$ 403

€ 356

Assessment, transfer taxes [Member]

Commitments and Contingencies

Assessed taxes including interest and penalties

43

39

Taxes Owed For Prior Periods

Commitments and Contingencies

Loss contingency accrual

67

75

$ 67

Estimated reasonably possible loss in excess of amount accrued

25

Italian Tax Audit

Commitments and Contingencies

Assessed taxes including interest and penalties

64

58

$ 52

€ 48

Payment required to appeal a litigation matter

$ 11

€ 10

Turkish Tax Audit

Commitments and Contingencies

Assessed taxes including interest and penalties

$ 83

₺ 544

Pension-related litigation [Member]

Commitments and Contingencies

Estimated reasonably possible loss in excess of amount accrued

$ 200

Manchester, England | Rentalcars.com | Headquarters

Commitments and Contingencies

Area of real estate property | ft²

222,000

222,000

Lease term of operating leases which have not commenced at period end

13 years

13 years

13 years

Manchester, England | Rentalcars.com | Headquarters | Operating Lease Obligations

Commitments and Contingencies

Contractual obligation

$ 80

£ 65

Subsequent Event | Booking.com | Headquarters

Commitments and Contingencies

Contractual obligation

$ 102

€ 93

OTHER - Reconciliation of Cash

OTHER - Reconciliation of Cash and Cash Equivalents and Restricted Cash and Cash Equivalents (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 6,363	$ 6,312
Restricted cash and cash equivalents included in Prepaid expenses and other current assets, net	20	20
Total cash and cash equivalents and restricted cash and cash equivalents as shown in the Unaudited Consolidated Statements of Cash Flows	$ 6,383	$ 6,332	$ 2,354	$ 2,645

OTHER - Narrative (Details)

OTHER - Narrative (Details) $ in Millions	Mar. 31, 2020USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Prepaid taxes	$ 717