Booking (BKNG) 10-Q 6 Aug 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Jul. 30, 2020
Entity Information [Line Items]
Document Type	10-Q
Document Fiscal Period Focus	Q2
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Amendment Flag	false
Document Fiscal Year Focus	2020
Current Fiscal Year End Date	--12-31
Entity File Number	1-36691
Entity Registrant Name	Booking Holdings Inc.
Entity Central Index Key	0001075531
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		40,948,631
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	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 10,404	$ 6,312
Short-term investments (Available-for-sale debt securities: Amortized cost of $998 at December 31, 2019)	0	998
Accounts receivable, net (Allowance for expected credit losses of $282 and $49, respectively)	566	1,680
Prepaid expenses and other current assets, net (Allowance for expected credit losses of $12 and $6, respectively)	483	843
Total current assets	11,453	9,833
Property and equipment, net	736	738
Operating lease assets	577	620
Intangible assets, net	1,865	1,954
Goodwill	2,412	2,913
Long-term investments (Includes available-for-sale debt securities: Amortized cost of $775 and $2,192, respectively)	2,946	4,477
Other assets, net (Allowance for expected credit losses of $44 at June 30, 2020)	923	867
Total assets	20,912	21,402
Current liabilities:
Accounts payable	581	1,239
Accrued expenses and other current liabilities	1,445	1,578
Deferred merchant bookings	910	1,561
Convertible debt	973	988
Total current liabilities	3,909	5,366
Deferred income taxes	931	876
Operating lease liabilities	417	462
Long-term U.S. transition tax liability	922	1,021
Other long-term liabilities	101	104
Long-term debt	10,633	7,640
Total liabilities	16,913	15,469
Commitments and Contingencies
Stockholders' equity:
Common stock, $0.008 par value, Authorized shares: 1,000,000,000 Issued shares: 63,390,891 and 63,179,471, respectively	0	0
Treasury stock, 22,442,328 and 21,762,070 shares, respectively	(24,119)	(22,864)
Additional paid-in capital	5,699	5,756
Retained earnings	22,652	23,232
Accumulated other comprehensive loss	(233)	(191)
Total stockholders' equity	3,999	5,933
Total liabilities and stockholders' equity	$ 20,912	$ 21,402

UNAUDITED CONSOLIDATED BALANC_2

UNAUDITED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Accounts receivable, allowance for credit loss	$ 282	$ 49
Prepaid expense, allowance for credit loss	$ 56	$ 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)	63,390,891	63,179,471
Treasury stock, shares (in shares)	22,442,328	21,762,070
Short-term Investments
Amortized cost of available-for-sale debt securities	$ 0	$ 998
Prepaid Expenses and Other Current Assets
Prepaid expense, allowance for credit loss	12	6
Long-term Investments
Amortized cost of available-for-sale debt securities	775	2,192
Other Assets [Member]
Prepaid expense, allowance for credit loss	$ 44	$ 0

UNAUDITED CONSOLIDATED STATEMEN

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Total revenues	$ 630	$ 3,850	$ 2,918	$ 6,687
Operating expenses:
Marketing expenses	211	1,367	1,062	2,560
Sales and other expenses	131	248	508	463
Personnel, including stock-based compensation of $77, $79, $83 and $153, respectively	452	619	936	1,120
General and administrative	104	180	305	371
Information technology	70	70	148	135
Depreciation and amortization	112	119	229	235
Restructuring and other exit costs	34	0	34	0
Impairment of goodwill	0	0	489	0
Total operating expenses	1,114	2,603	3,711	4,884
Operating (loss) income	(484)	1,247	(793)	1,803
Other income (expense):
Interest income	12	34	44	69
Interest expense	(96)	(68)	(160)	(134)
Net gains/(losses) on marketable equity securities	835	17	528	468
Impairment of investment	0	0	(100)	0
Foreign currency transactions and other	(58)	(23)	(32)	(31)
Total other income (expense)	693	(40)	280	372
Income (loss) before income taxes	209	1,207	(513)	2,175
Income tax expense	87	228	64	431
Net income (loss)	$ 122	$ 979	$ (577)	$ 1,744
Net income applicable to common stockholders per basic common share (in dollars per share)	$ 2.98	$ 22.62	$ (14.07)	$ 39.52
Weighted-average number of basic common shares outstanding (in shares)	40,922	43,251	41,007	44,124
Net income applicable to common stockholders per diluted common share (in dollars per share)	$ 2.97	$ 22.44	$ (14.07)	$ 39.17
Weighted-average number of diluted common shares outstanding (in shares)	40,995	43,601	41,007	44,514
Agency revenues
Total revenues	$ 357	$ 2,607	$ 1,781	$ 4,556
Merchant revenues
Total revenues	245	959	904	1,562
Advertising and other revenues
Total revenues	$ 28	$ 284	$ 233	$ 569

UNAUDITED CONSOLIDATED STATEM_2

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Stock-based compensation expense	$ 77	$ 79	$ 83	$ 153

UNAUDITED CONSOLIDATED STATEM_3

UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Other comprehensive income (loss), net of tax
Net (loss) income	$ 122	$ 979	$ (577)	$ 1,744
Foreign currency translation adjustments, net of tax	32	(16)	(45)	(28)
Net unrealized gains (losses) on available-for-sale securities, net of tax	77	(45)	3	114
Total other comprehensive income (loss), net of tax	109	(61)	(42)	86
Comprehensive income (loss)	$ 231	$ 918	$ (619)	$ 1,830

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	1,744				1,744
Foreign currency translation adjustments, net of tax	(28)					(28)
Net unrealized gains on available-for-sale securities, net of tax	114					114
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)		195
Exercise of stock options and vesting of restricted stock units and performance share units	$ 1	$ 0		1
Repurchase of common stock (in shares)	(3,061)		(3,061)
Repurchase of common stock	$ (5,462)		$ (5,462)
Stock-based compensation and other stock-based payments	153			153
Balance (in shares) at Jun. 30, 2019		63,144	(20,378)
Balance at Jun. 30, 2019	5,307	$ 0	$ (20,173)	5,599	20,111	(230)
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)
Increase (Decrease) in Stockholders' Equity
Net (loss) income	979				979
Foreign currency translation adjustments, net of tax	(16)					(16)
Net unrealized gains on available-for-sale securities, net of tax	(45)					(45)
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)		22
Exercise of stock options and vesting of restricted stock units and performance share units	$ 1	$ 0		1
Repurchase of common stock (in shares)	(1,442)		(1,442)
Repurchase of common stock	$ (2,606)		$ (2,606)
Stock-based compensation and other stock-based payments	79			79
Balance (in shares) at Jun. 30, 2019		63,144	(20,378)
Balance at Jun. 30, 2019	5,307	$ 0	$ (20,173)	5,599	20,111	(230)
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	(577)				(577)
Foreign currency translation adjustments, net of tax	(45)					(45)
Net unrealized gains on available-for-sale securities, net of tax	3					3
Issuance of convertible senior notes	96			96
Conversion of debt	(245)			(245)
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)		212
Exercise of stock options and vesting of restricted stock units and performance share units	$ 6	$ 0		6
Repurchase of common stock (in shares)	(680)		(680)
Repurchase of common stock	$ (1,255)		$ (1,255)
Stock-based compensation and other stock-based payments	86			86
Balance (in shares) at Jun. 30, 2020		63,391	(22,442)
Balance at Jun. 30, 2020	3,999	$ 0	$ (24,119)	5,699	22,652	(233)
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)
Increase (Decrease) in Stockholders' Equity
Net (loss) income	122				122
Foreign currency translation adjustments, net of tax	32					32
Net unrealized gains on available-for-sale securities, net of tax	77					77
Issuance of convertible senior notes	96			96
Conversion of debt	(241)			(241)
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)		21
Exercise of stock options and vesting of restricted stock units and performance share units	$ 6	$ 0		6
Repurchase of common stock (in shares)	(2)		(2)
Repurchase of common stock	$ (4)		$ (4)
Stock-based compensation and other stock-based payments	80			80
Balance (in shares) at Jun. 30, 2020		63,391	(22,442)
Balance at Jun. 30, 2020	$ 3,999	$ 0	$ (24,119)	$ 5,699	$ 22,652	$ (233)

UNAUDITED CONSOLIDATED STATEM_5

UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
OPERATING ACTIVITIES:
Net (loss) income	$ (577)	$ 1,744
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Depreciation and amortization	229	235
Provision for expected credit losses and chargebacks	322	74
Deferred income tax expense	11	60
Net gains on marketable equity securities	(528)	(468)
Stock-based compensation expense and other stock-based payments	94	162
Operating lease amortization	91	85
Amortization of debt discount and debt issuance costs	33	28
Unrealized foreign currency transaction losses on Euro-denominated debt	22	19
Impairment of goodwill	489	0
Impairment of investment	100	0
Other	3	9
Changes in assets and liabilities, net of effect of acquisition:
Accounts receivable	805	(523)
Prepaid expenses and other current assets	248	(584)
Deferred merchant bookings and other current liabilities	(1,567)	1,513
Other long-term assets and liabilities	(33)	(417)
Net cash (used in) provided by operating activities	(258)	1,937
INVESTING ACTIVITIES:
Purchase of investments	(72)	(580)
Proceeds from sale and maturity of investments	2,997	6,977
Additions to property and equipment	(150)	(199)
Acquisitions and other investments, net of cash acquired	0	(9)
Net cash provided by investing activities	2,775	6,189
FINANCING ACTIVITIES:
Proceeds from revolving credit facility and short-term borrowings	56	437
Repayments of revolving credit facility and short-term borrowings	0	(425)
Proceeds from the issuance of long-term debt	4,108	0
Payments of debt issuance costs	(38)	0
Payments for conversion of debt	(1,244)	0
Payments for repurchase of common stock	(1,294)	(5,491)
Other financing activities	5	(8)
Net cash provided by (used in) financing activities	1,593	(5,487)
Effect of exchange rate changes on cash and cash equivalents and restricted cash and cash equivalents	(19)	(8)
Net increase in cash and cash equivalents and restricted cash and cash equivalents	4,091	2,631
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)	10,423	5,276
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid during the period for income taxes (see Note 14)	61	949
Cash paid during the period for interest	$ 92	$ 101

BASIS OF PRESENTATION (Notes)

BASIS OF PRESENTATION (Notes)	6 Months Ended
	Jun. 30, 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, including quarantine restrictions after travel in certain locations, shelter-in-place orders, required closures of non-essential businesses and additional restrictions on businesses as part of re-opening plans. 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, to file for bankruptcy protection 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 each of the quarters ended March 31, 2020 and June 30, 2020 have been significantly and negatively impacted as compared to the corresponding periods in 2019. The impact of COVID-19 pandemic for the quarter ended June 30, 2020, is more significant than for the quarter ended March 31, 2020, primarily because an increasing number of markets and locations 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). 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. With the spread of COVID-19 to all major regions, 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, during any resurgence 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 may 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 determined that a portion of its goodwill had experienced a decline in value at March 31, 2020 and recorded a significant impairment charge (see Note 8). In addition, the Company recorded a significant impairment charge at March 31, 2020 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). Even though no additional impairment indicators were identified as of June 30, 2020 for these assets, it is possible that the Company may 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 ability to meet debt covenant requirements, 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. In response to the reduction in the Company's business volumes as a result of the impact of the COVID-19 pandemic, the Company has taken actions to reduce the size of its workforce to optimize efficiency. See Note 14 for additional information. Certain governments have passed or are considering legislation to help businesses during the COVID-19 pandemic through loans, wage subsidies, tax relief or other financial aid, and some of these governments have extended or are considering extending these programs. The Company has participated in several of these programs, including the Netherlands' wage subsidy program, the United Kingdom's job retention scheme and certain other jurisdictions' programs. See Note 14 for additional information. 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 Consolidated Statements of Operations for the three and six months ended June 30, 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 additional 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 expected 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 additional information related to allowance for expected credit losses on accounts receivable and other financial assets and Note 5 for additional information related to investments in available-for-sale debt securities. Other Recent Accounting Pronouncement Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity In August 2020, the FASB issued a new accounting update relating to convertible instruments and contracts in an entity’s own equity. For convertible instruments, the accounting update reduces the number of accounting models for convertible debt instruments and convertible preferred stock. Limiting the accounting models results in fewer embedded conversion features being separately recognized from the host contract as compared with current GAAP. The accounting update amends the guidance for the derivatives scope exception for contracts in an entity’s own equity to reduce form-over-substance-based accounting conclusions. The accounting update also simplifies the diluted earnings per share calculation in certain areas. For public business entities, the update is effective for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years. Early adoption is permitted for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years. The Company is currently evaluating the impact to its Consolidated Financial Statements of adopting this update. 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. For public business entities, this update is effective for fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. Early adoption is permitted. The amendment related to franchise taxes that are partially based on income should be applied on either a retrospective basis for all periods presented or a modified retrospective basis through a cumulative-effect adjustment to retained earnings as of the beginning of the fiscal year of adoption. All other

REVENUE (Notes)

REVENUE (Notes)	6 Months Ended
	Jun. 30, 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 June 30, 2020 $ 105 $ 444 $ 81 $ 630 2019 (1) 400 2,997 453 3,850 Total revenues for the six months ended June 30, 2020 $ 390 $ 2,121 $ 407 $ 2,918 2019 (1) 766 5,069 852 6,687 (1) Geographic information for the three and six months ended June 30, 2019 has been recast to conform to the current period presentation. Revenue by Type of Service Approximately 86% and 85% of the Company's revenue for the three and six months ended June 30, 2020, respectively, and 87% and 86% of the Company's revenue for the three and six months ended June 30, 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 six months ended June 30, 2020 (in millions): Balance, December 31, 2019 $ 220 Revenues recognized from the beginning deferred revenue balance (147) Cancellations and amendments (61) Payments received from travelers, net of amounts estimated to be payable to travel service providers, and other 137 Balance, June 30, 2020 $ 149 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 June 30, 2020 and December 31, 2019, liabilities for loyalty program incentives of $67 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 platforms. 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 June 30, 2020 and December 31, 2019, liabilities of $30 million and $22 million, respectively, 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 may 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 six months ended June 30, 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 (Notes)	6 Months Ended
	Jun. 30, 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 $77 million and $79 million for the three months ended June 30, 2020 and 2019, respectively, and $83 million and $153 million for the six months ended June 30, 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 is determined using the Black-Scholes model. Performance share units and restricted stock units are payable in shares of the Company's common stock upon vesting. The Company issues shares of its common stock upon the exercise of stock options. 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 was a significant decline in the estimated performance over the performance periods against the performance targets and consequently, 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 for the six months ended June 30, 2020. During the three months ended June 30, 2020, considering pre-COVID-19 performance and the significant effect of the COVID-19 pandemic on Company performance and consequently on the number of shares that were probable to be issued to employees, the Company modified the performance-based awards granted in 2018 (other than the performance-based awards granted to executive officers and certain other employees) to fix the number of shares to be issued, subject to other vesting conditions. As a result, the Company incurred an additional stock-based compensation expense of $11 million to be recognized over the remaining requisite service period. Restricted stock units granted by the Company during the three and six months ended June 30, 2020 had aggregate grant-date fair values of $85 million and $350 million, respectively. Restricted stock units and performance share units that vested during the three and six months ended June 30, 2020 had aggregate fair values at vesting of $14 million and $333 million, respectively. At June 30, 2020, there was $542 million of estimated total future stock-based compensation expense related to unvested restricted stock units and performance share units to be recognized over a weighted-average period of 2.2 years. Stock options granted by the Company during the three and six months ended June 30, 2020 had an aggregate grant-date fair value of $79 million. At June 30, 2020, there was $75 million of estimated total future stock-based compensation expense related to unvested stock options to be recognized over a weighted-average period of 2.7 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 six months ended June 30, 2020: Restricted Stock Units Shares Weighted-average Grant-date Fair Value Per Share Unvested at December 31, 2019 256,745 $ 1,801 Granted 212,913 $ 1,644 Vested (117,709) $ 1,811 Forfeited (15,636) $ 1,784 Unvested at June 30, 2020 336,313 $ 1,698 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. The number of shares that ultimately 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 six months ended June 30, 2020: Performance Share Units Shares Weighted-average Grant-date Fair Value Per Share Unvested at December 31, 2019 216,083 $ 1,835 Vested (81,396) $ 1,740 Performance Shares Adjustment * (50,182) $ 1,944 Forfeited (4,547) $ 1,840 Unvested at June 30, 2020 79,958 $ 1,859 * Probable outcome for these performance-based awards is updated based upon changes in actual and forecasted operating results and the impact of modifications. No performance share units were granted during the six months ended June 30, 2020. The following table summarizes the estimated vesting, as of June 30, 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 44,237 35,721 Shares not subject to the achievement of minimum performance thresholds 44,237 35,721 Shares that could be issued if maximum performance thresholds are met 115,310 62,606 Stock Options In May 2020, the Company granted stock options that vest in March 2023, subject to certain exceptions for terminations other than for "cause," for "good reason" or on account of death or disability. No stock options were granted to the executive officers of the Company. Stock options granted or assumed in acquisitions generally have a term of 10 years from the grant date. The fair value of stock options granted is estimated on the grant date using the Black-Scholes option pricing model and is affected by assumptions regarding a number of complex and subjective variables. The use of an option pricing model requires the use of several assumptions including expected volatility, risk-free interest rate, expected dividends, and expected term. Expected volatility is based on the Company’s historical volatility over the expected term of the option and implied volatility of publicly traded options of the Company’s common stock. The expected term of the options represents the estimated period of time until option exercise. Since the Company has limited historical stock option exercise experience, the Company used the simplified method in estimating the expected term, which is calculated as the average of the sum of the vesting term and the original contractual term of the options. The risk-free interest rate is based on U.S. Treasury zero-coupon issues at the time of grant for the expected term of the option. The following table summarizes the assumptions used to value option grants granted in the six months ended June 30, 2020 using the Black-Scholes options pricing model: Black-Scholes assumptions Risk-free interest rate 0.56 % Expected term in years 6.4 Expected stock price volatility 33.8 % Expected dividend yield 0 % The following table summarizes the activity for stock options during the six months ended June 30, 2020: Employee Stock Options Number of Shares Weighted-average Aggregate Weighted-average Remaining Contractual Term Balance, December 31, 2019 15,122 $ 484 $ 24 2.6 Granted 163,494 $ 1,411 Exercised (12,884) $ 464 Forfeited (690) $ 1,411 Balance, June 30, 2020 165,042 $ 1,400 $ 32 9.8 Exercisable at June 30, 2020 2,238 $ 616 $ 2 2.5 Stock options granted by the Company during the six months ended June 30, 2020 had a weighted-average grant-date fair value per option of $485. The aggregate intrinsic value of employee stock options exercised during the six months ended June 30, 2020 and 2019 was $14 million and $2 million, respectively.

NET INCOME PER SHARE (Notes)

NET INCOME PER SHARE (Notes)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
NET INCOME PER SHARE	NET INCOME (LOSS) PER SHARE The Company computes basic net income (loss) per share by dividing net income (loss) 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 income (loss) per share is as follows (in thousands): Three Months Ended Six Months Ended 2020 2019 2020 2019 Weighted-average number of basic common shares outstanding 40,922 43,251 41,007 44,124 Weighted-average dilutive stock options, restricted stock units and performance share units 73 146 — 188 Assumed conversion of convertible senior notes — 204 — 202 Weighted-average number of diluted common and common equivalent shares outstanding 40,995 43,601 41,007 44,514 For the three and six months ended June 30, 2020, 334,000 and 166,000 potential common shares, respectively, related to stock options, restricted stock units, performance share units and convertible senior notes were excluded from the calculation of diluted net income (loss) per share because their effect would have been anti-dilutive for the perio

INVESTMENTS (Notes)

INVESTMENTS (Notes)	6 Months Ended
	Jun. 30, 2020
Investments, Debt and Equity Securities [Abstract]
INVESTMENTS	INVESTMENTS The following table summarizes, by major security type, the Company's investments at June 30, 2020 (in millions): Cost Gross Gross Carrying Value Long-term investments: Investments in private companies: Debt securities $ 250 $ — $ — $ 250 Equity securities 501 — (100) 401 Other long-term investments: Debt securities: Trip.com Group convertible debt securities 525 — (25) 500 Equity securities 461 1,336 (2) 1,795 Total $ 1,737 $ 1,336 $ (127) $ 2,946 The following table summarizes, by major security type, the Company's investments at December 31, 2019 (in millions): Cost Gross Gross Unrealized Losses/Downward Adjustments 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. 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 expected 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 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. During the six months ended June 30, 2020, the Company realized $2.2 billion in cash from the sales and maturities of its investments in government and corporate debt securities. Investments in Trip.com Group At June 30, 2020, the Company had $525 million invested in convertible senior notes issued at par value by Trip.com Group maturing in September 2022 and December 2025. The strategic investments in Trip.com Group convertible senior notes were classified as "Long-term investments" in the Consolidated Balance Sheet at June 30, 2020. In May 2020, the Company's May 2015 investment of $250 million in Trip.com Group's convertible notes was repaid upon maturity. At June 30, 2020, the estimated fair values of the Company’s investments in the convertible notes were lower than their respective amortized cost basis. At June 30, 2020, the Company did not have the intent or a requirement to sell its investment in Trip.com Group convertible notes 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 June 30, 2020 expects recovery of the amortized cost basis of the investments. 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. At December 31, 2019, the Company had $655 million invested in Trip.com Group American Depositary Shares ("ADSs") with a fair value of $726 million, which is reported in "Long-term investments" in the Consolidated Balance Sheet. In the six months ended June 30, 2020, the Company sold its entire investment in these ADSs for $525 million. "Net gains on marketable equity securities" in the Unaudited Consolidated Statement of Operations for the three and six months ended June 30, 2020 includes a net realized gain of $17 million and a net realized loss of $201 million, respectively, related to the sale of ADSs. "Net gains on marketable equity securities" in the Unaudited Consolidated Statements of Operations included a net unrealized loss of $147 million and a net unrealized gain of $213 million for the three and six months ended June 30, 2019, respectively, related to the Company's investment in these ADSs. 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 $1.8 billion and $1.1 billion at June 30, 2020 and December 31, 2019, respectively, which is included in "Long-term investments" in the Consolidated Balance Sheets. Net unrealized gains of $813 million and $732 million for the three and six months ended June 30, 2020, respectively, and net unrealized gains of $164 million and $255 million for the three and six months ended June 30, 2019, respectively, related to this investment, are included in "Net 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 June 30, 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, as of March 31, 2020, on the investment in Didi Chuxing. The Company recognized an impairment charge of $100 million in the three months ended March 31, 2020, resulting in an adjusted carrying value of $400 million at March 31, 2020 and June 30, 2020 (see Note 6). No additional impairment indicators were identified as of June 30, 2020. Debt Securities The Company had $250 million invested in preferred shares of private companies, including Grab Holdings Inc. ("Grab"), with an aggregate estimated fair value of $250 million at both June 30, 2020 and December 31, 2019. 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 estimated fair value of the Company's investment in Grab was $200 million at both June 30, 2020 and December 31, 2019. The Company recognized an unrealized loss of $20 million in the three months ended March 31, 2020 and

FAIR VALUE MEASUREMENTS (Notes)

FAIR VALUE MEASUREMENTS (Notes)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS Financial assets and liabilities carried at fair value at June 30, 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 fund investments $ 10,089 $ — $ — $ 10,089 Time deposits and certificates of deposit 25 — — 25 Long-term investments: Investments in private companies: Debt securities — — 250 250 Other long-term investments: Trip.com Group convertible debt securities — 500 — 500 Equity securities 1,795 — — 1,795 Derivatives: Foreign currency exchange derivatives — 4 — 4 Total assets at fair value $ 11,909 $ 504 $ 250 $ 12,663 LIABILITIES: Foreign currency exchange derivatives $ — $ 3 $ — $ 3 Nonrecurring fair value measurements Investment in Didi Chuxing (1) $ — $ — $ 400 $ 400 Goodwill of the OpenTable and KAYAK reporting unit (2) — — 1,545 1,545 Total nonrecurring fair value measurements $ — $ — $ 1,945 $ 1,945 (1) At March 31, 2020, the investment in DiDi Chuxing was written down to its estimated fair value of $400 million, resulting in an impairment charge of $100 million (see Note 5). (2) At March 31, 2020, the goodwill of OpenTable and KAYAK reporting unit was written down to its estimated fair value of $1.5 billion, resulting in an impairment charge of $489 million (see Note 8). 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 fund investments $ 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. Investments See Note 5 for additional 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. The Company's investments in private companies accounted for as debt securities had an aggregate estimated fair value of $250 million at June 30, 2020, which includes the Company's investment in Grab with an estimated fair value of $200 million. The Company measured these investments using Level 3 inputs and management's estimates that incorporate current market participant expectations of future cash flows considered alongside recent financing transactions of the investees and other relevant information. For the investment in equity securities of Didi Chuxing, considering the impact of the COVID-19 pandemic, the Company performed an impairment analysis as of March 31, 2020 resulting in an adjusted carrying value of $400 million at March 31, 2020 and June 30, 2020. No additional impairment indicators were identified as of June 30, 2020. 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 Chuxing. 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 include the weighted average cost of capital (12%-14%), terminal Earnings before income taxes, depreciation and amortization (“EBITDA”) Multiple (13x-15x), 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 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. In periods prior to the second quarter of 2020, the Company also entered 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. In the second quarter of 2020, the Company did not enter into such derivative instruments as the impact of the COVID-19 pandemic on the Company’s operating results were highly uncertain. 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 June 30, 2020 and December 31, 2019, the Company did not designate any derivatives as hedges for accounting purposes. The table below provides estimated fair values and notional amounts of foreign currency exchange derivatives outstanding at June 30, 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. June 30, 2020 December 31, 2019 Estimated fair value of derivative assets $ 4 $ 12 Estimated fair value of derivative liabilities 3 5 Notional amount: Foreign currency purchases 1,050 1,770 Foreign currency sales 636 901 The effect of foreign currency exchange derivatives recorded in "Foreign currency transactions and other" in the Unaudited Consolidated Statements of Operations for the three and six months ended June 30, 2020 and 2019 is as follows (in millions): Three Months Ended Six Months Ended 2020 2019 2020 2019 (Losses) gains on foreign currency exchange derivatives $ (8) $ 8 $ (31) $ (5) Other Financial Assets and Liabilities At June 30, 2020 and December 31, 2019, the Company's cash consisted of bank deposits. Cash equivalents principally include money market fund investments, time deposits and certificates of deposit. 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

ACCOUNTS RECEIVABLE AND OTHER F

ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS (Notes)	6 Months Ended
	Jun. 30, 2020
Receivables [Abstract]
ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS	ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS Accounts receivable in the Consolidated Balance Sheets at June 30, 2020 and December 31, 2019 includes receivables from customers of $620 million and $1.2 billion, respectively, and receivables from marketing affiliates of $32 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 $130 million and $232 million at June 30, 2020 and December 31, 2019, respectively, which are included in "Prepaid expenses and other current assets, net," and $80 million at June 30, 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 expected 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): Six Months Ended 2020 2019 Balance, beginning of year $ 49 $ 51 Provision charged to earnings 241 38 Write-offs and adjustments (11) (40) Currency translation adjustments 3 (1) Balance, end of period $ 282 $ 48 The allowance for expected credit losses on receivables as of June 30, 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 six months ended June 30, 2020, the Company recorded a reduction in revenue of $55 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 $56 million and $6 million at June 30, 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. Expected credit loss expenses included in "Sales and other expenses" in the Unaudited Consolidated Statements of Operations, increased from $38 million for the six months ended June 30, 2019 to $233 million for the six months ended June 30, 2020. 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 (Notes)	6 Months Ended
	Jun. 30, 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 six months ended June 30, 2020 consist of the following (in millions): Balance, December 31, 2019 (1) $ 2,913 Impairment (489) Foreign currency translation adjustments (12) Balance, June 30, 2020 (1) $ 2,412 (1) The balance of goodwill as of June 30, 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). No additional impairment indicators were identified as of June 30, 2020. As of March 31, 2020, the estimated 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 for the three months ended March 31, 2020, 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 cash flow projections. In the cash flow projections, 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 June 30, 2020 and December 31, 2019 consist of the following (in millions): June 30, 2020 December 31, 2019 Gross Accumulated Net Gross Accumulated Net Amortization Supply and distribution agreements $ 1,094 $ (498) $ 596 $ 1,100 $ (472) $ 628 3 - 20 years Technology 170 (135) 35 170 (129) 41 2 - 7 years Internet domain names 39 (33) 6 40 (32) 8 5 - 20 years Trade names 1,808 (580) 1,228 1,811 (534) 1,277 4 - 20 years Other intangible assets 2 (2) — 2 (2) — Up to 15 years Total intangible assets $ 3,113 $ (1,248) $ 1,865 $ 3,123 $ (1,169) $ 1,954 Intangible assets are amortized on a straight-line basis. Amortization expense was $42 million and $85 million for the three and six months ended June 30, 2020, respectively, and $44 million and $89 million for the three and six months ended June 30, 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), at March 31, 2020, the Company performed the recoverability test of its long-lived assets and concluded that there was no impairment. No additional impairment indicators were identified as of June 30, 2020.

DEBT (Notes)

DEBT (Notes)	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
DEBT	DEBT Short-term Borrowings On June 30, 2020, the Company had bank overdrafts of $56 million, which were repaid in July 2020. The bank overdrafts are reported in "Accrued expenses and other current liabilities" in the Consolidated Balance Sheet at June 30, 2020 . 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 $3 million and $5 million of letters of credit issued under this revolving credit facility at June 30, 2020 and December 31, 2019, respectively. 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 six months ended June 30, 2019, the Company made short-term borrowings under the prior revolving credit facility totaling $400 million with a weighted-average interest rate of 3.5%, which were repaid prior to 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 June 30, 2020 consists of the following (in millions): June 30, 2020 Outstanding Principal Amount Unamortized Debt Carrying Value Current liabilities: 0.9% Convertible Senior Notes due September 2021 $ 1,000 $ (27) $ 973 Long-term debt: 0.8% (€1 Billion) Senior Notes due March 2022 $ 1,123 $ (2) $ 1,121 2.15% (€750 Million) Senior Notes due November 2022 842 (1) 841 2.75% Senior Notes due March 2023 500 (2) 498 2.375% (€1 Billion) Senior Notes due September 2024 1,123 (8) 1,115 3.65% Senior Notes due March 2025 500 (2) 498 4.1% Senior Notes due April 2025 1,000 (5) 995 0.75% Convertible Senior Notes due May 2025 863 (141) 722 3.6% Senior Notes due June 2026 1,000 (5) 995 1.8% (€1 Billion) Senior Notes due March 2027 1,123 (4) 1,119 4.5% Senior Notes due April 2027 750 (6) 744 3.55% Senior Notes due March 2028 500 (3) 497 4.625% Senior Notes due April 2030 1,500 (12) 1,488 Total long-term debt $ 10,824 $ (191) $ 10,633 Outstanding debt at December 31, 2019 consists of the following (in millions): December 31, 2019 Outstanding Unamortized Debt 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 June 30, 2020 and December 31, 2019, the contingent conversion threshold on the 2021 Notes (as defined below) was not exceeded and therefore the notes were not convertible at the option of the holders. The 2021 Notes were reported as non-current liabilities in the Consolidated Balance Sheet at December 31, 2019 and reclassified as current liabilities at June 30, 2020 since the holders will have the right to convert all or any portion of the 2021 Notes starting on June 15, 2021 regardless of the Company's stock price. Fair Value of Debt At June 30, 2020 and December 31, 2019, the estimated fair value of the outstanding Senior Notes was approximately $13.0 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 estimated fair value of the Company's debt in excess of the outstanding principal amount primarily relates to the Senior Notes and the Convertible Senior Notes issued in April 2020. 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 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 Company paid $19 million in debt issuance costs during the three months ended June 30, 2020 related to this offering. 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 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 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 $235 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. At June 30, 2020, the if-converted value of the May 2025 Notes was lower than the aggregate principal amount. The proceeds from the issuance of the Convertible 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 outstanding 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 June 30, 2020, the if-converted value of the 2021 Notes was lower than the aggregate principal 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"). In June 2020, in connection with the maturity of the outstanding 2020 Notes, the Company paid $1.0 billion to satisfy the aggregate principal amount due and paid an additional $245 million in satisfaction of the conversion value in excess of the principal amount. 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 4.10% for the May 2025 Notes, 3.18% for the 2021 Notes and 3.13% for the 2020 Notes, considering its credit rating and similar debt of the Company or 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 $100 million ($130 million before tax) related to the May 2025 Notes, $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 allocated to the equity component of the respective convertible notes was recorded in "Additional paid-in capital" in the balance sheet at debt origination. For the three months ended June 30, 2020 and 2019, the Company recognized interest expense of $21 million and $16 million, respectively, related to convertible notes, which is almost entirely comprised of the amortization of debt discount of $15 million and $12 million, respectively, and the contractual coupon interest of $4 million and $3 million, respectively. For the three months ended June 30, 2019, included in the amortization of debt discount mentioned above is $1 million of original issuance discount related to the 2020 Notes. The remaining interest expense relates to the amortization of debt issuance costs. The weighted-average effective interest rate for both the three months ended June 30, 2020 and 2019 was 3.2%. For the six months ended June 30, 2020 and 2019, the Company recognized interest expense of $36 million and $31 million, respectively, related to convertible notes, which was almost entirely comprised of the amortization of debt discount of $27 million and $24 million, respectively, and the contractual coupon interest of $7 million and $6 million, respectively. For the six months ended June 30, 2020 and 2019, included in the amortization of debt discount mentioned above was $1 million and $2 million of original issuance discount, respectively, related to the 2020 Notes. The remaining interest expense related 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 the six months ended June 30, 2020 and 2019 were 3.3% and 3.2%, respectively. Other Long-term Debt 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 $1.0 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. 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 outstanding Convertible Senior Notes. Other long-term debt, including the Senior Notes issued in April 2020, had a total carrying value of $9.9 billion and $6.7 billion at June 30, 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 outstanding at June 30, 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 4.1% Senior Notes due April 2025 April 2020 4.10 % Semi-annually in April and October 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 4.5% Senior Notes due April 2027 April 2020 4.54 % Semi-annually in April and October 3.55% Senior Notes due March 2028 August 2017 3.56 % Semi-annually in March and September 4.625% Senior Notes due April 2030 April 2020 4.65 % Semi-annually in April and October For the three months ended June 30, 2020 and 2019, the Company recognized interest expense of $72 million and $41 million, respectively, related to other long-term debt, which is almost entirely comprised of $70 million and $40 million, respectively, related to the contractual coupon interest. The remaining interest expense relates to the amortization of debt discount and debt issuance costs. For the six months ended June 30, 2020 and 2019, the Company recognized interest expense of $114 million and $83 million, respectively, related to other long-term debt, which was almost entirely comprised of $110 million and $80 million, respectively, related to the contractual coupon interest. The remaining interest expense related 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.

TREASURY STOCK (Notes)

TREASURY STOCK (Notes)	6 Months Ended
	Jun. 30, 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 June 30, 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 the third quarter of 2020 to date under this authorization and does not intend to initiate any repurchases under this authorization 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 and six months ended June 30, 2020 and 2019 (in millions, except for shares, which are reflected in thousands): Three Months Ended Six Months Ended 2020 2019 2020 2019 Shares Amount Shares Amount Shares Amount Shares Amount Authorized stock repurchase programs — $ — 1,434 $ 2,590 601 $ 1,122 2,982 $ 5,325 General authorization for shares withheld on stock award vesting 2 4 8 16 79 133 79 137 Total 2 $ 4 1,442 $ 2,606 680 $ 1,255 3,061 $ 5,462 Stock repurchases of $40 million in December 2019 were settled in January 2020. For the six months ended June 30, 2020 and 2019, the Company remitted employee withholding taxes of $132 million and $136 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 June 30, 2020, there were 22,442,328 shares of the Company's common stock held in treasury.

INCOME TAXES (Notes)

INCOME TAXES (Notes)	6 Months Ended
	Jun. 30, 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 rates for the three and six months ended June 30, 2020 were 41.4% and (12.4)%, respectively, compared to 18.9% and 19.8% for the three and six months ended June 30, 2019, respectively. The Company's 2020 effective tax rates differ from the U.S. federal statutory tax rate of 21%, primarily due to the non-deductible goodwill impairment charge related to OpenTable and KAYAK, certain non-deductible expenses relative to lower worldwide earnings, and the valuation allowance recorded against the deferred tax assets generated from the impairment of certain long-term investments, partially offset by the benefit of the Netherlands Innovation Box Tax (discussed below) and U.S. state tax benefits. The Company's 2019 effective tax rates differ from the U.S. federal statutory tax rate of 21%, primarily due to the benefit of the Netherlands Innovation Box Tax, partially offset by the effect of higher international tax rates. The Company's effective tax rate for the three months ended June 30, 2020 was higher than the three months ended June 30, 2019, primarily due to discrete U.S. tax charges related to unrealized gains on equity securities, as well as certain non-deductible expenses relative to lower worldwide earnings, partially offset by higher U.S. state tax benefits.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME (Notes)	6 Months Ended
	Jun. 30, 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 and six months ended June 30, 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) benefit Three Months Ended June 30, 2020 Balance, March 31, 2020 $ (314) $ 58 $ 60 $ (20) $ (216) $ (97) $ (29) $ (126) $ (342) Other Comprehensive Income (Loss) ("OCI") before reclassifications 65 — (43) 10 32 73 (11) 62 94 Amounts reclassified to net income (3) — — — — — — 15 15 15 OCI for the period 65 — (43) 10 32 73 4 77 109 Balance, June 30, 2020 $ (249) $ 58 $ 17 $ (10) $ (184) $ (24) $ (25) $ (49) $ (233) Six Months Ended June 30, 2020 Balance, December 31, 2019 $ (186) $ 54 $ (2) $ (5) $ (139) $ (7) $ (45) $ (52) $ (191) OCI before reclassifications (63) 4 19 (5) (45) (21) 6 (15) (60) Amounts reclassified to net income (3) — — — — — 4 14 18 18 OCI for the period (63) 4 19 (5) (45) (17) 20 3 (42) Balance, June 30, 2020 $ (249) $ 58 $ 17 $ (10) $ (184) $ (24) $ (25) $ (49) $ (233) 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) benefit Three Months Ended June 30, 2019 Balance, March 31, 2019 $ (189) $ 52 $ 3 $ (7) $ (141) $ 53 $ (81) $ (28) $ (169) OCI before reclassifications 10 4 (41) 11 (16) (50) 14 (36) (52) Amounts reclassified to net income (3) — — — — — (10) 1 (9) (9) OCI for the period 10 4 (41) 11 (16) (60) 15 (45) (61) Balance, June 30, 2019 $ (179) $ 56 $ (38) $ 4 $ (157) $ (7) $ (66) $ (73) $ (230) Six Months Ended June 30, 2019 Balance, December 31, 2018 $ (109) $ 41 $ (73) $ 12 $ (129) $ (157) $ (30) $ (187) $ (316) OCI before reclassifications (70) 15 35 (8) (28) 161 (37) 124 96 Amounts reclassified to net income (3) — — — — — (11) 1 (10) (10) OCI for the period (70) 15 35 (8) (28) 150 (36) 114 86 Balance, June 30, 2019 $ (179) $ 56 $ (38) $ 4 $ (157) $ (7) $ (66) $ (73) $ (230) (1) Net investment hedges balance, net of tax, at June 30, 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) gains before tax from sales of investments in debt securities and impairment losses before tax related to debt securities are included in "Foreign currency transactions and other" and the related reclassified tax benefits (expenses) are included in "Income tax 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. For the three and six months ended June 30, 2020, the reclassified tax expenses includes a tax expense of $15 million related to the maturity in May 2020 of the Company's investment of $250 million in Trip.com Group convertible notes (see Note 5).

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Notes)	6 Months Ended
	Jun. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Competition and Consumer Protection Reviews At times, online platforms, including online travel platforms, have been the subject of investigations or inquiries by various national competition authorities ("NCAs") or other governmental authorities regarding competition law matters, consumer protection issues or other areas of concern. The Company is or has been involved in many such investigations. For example, the Company has been and continues to be involved in investigations related to whether Booking.com's contractual parity arrangements with accommodation providers, sometimes also referred to as "most favored nation" or "MFN" provisions, are anti-competitive because they require accommodation providers to provide Booking.com with room rates, conditions or availability that are at least as favorable as those offered to other online travel companies ("OTCs") or through the accommodation provider's website. To resolve and close certain of the investigations, the Company has from time to time made commitments to the investigating authorities regarding future business practices or activities. For example, Booking.com has made commitments to several NCAs, including agreeing to narrow the scope of its parity clauses, in order to resolve parity-related investigations. In addition, in September 2017, the Swiss Price Surveillance Office opened an investigation into the level of commissions of Booking.com in Switzerland and the investigation is ongoing. If there is an adverse outcome and Booking.com is unsuccessful in any appeal, Booking.com could be required to reduce its commissions in Switzerland. Some authorities are reviewing the online hotel booking sector more generally through market inquiries and the Company cannot predict the outcome of such inquiries or any resulting impact on its business, results of operations, cash flows or financial condition. NCAs or other governmental authorities are continuing to review the activities of online platforms, including through the use of consumer protection powers. For example, the United Kingdom's NCA (the Competition and Markets Authority, or CMA) conducted a consumer protection law investigation into the clarity, accuracy and presentation of information on hotel booking sites. In connection with this investigation, in 2019 Booking.com, agoda and KAYAK, along with a number of other OTCs, voluntarily agreed to certain commitments with the CMA in resolution of this investigation without finding an infringement or an admission of wrongdoing by the OTCs involved. Among other things, the commitments provided to the CMA included showing prices inclusive of all mandatory taxes and charges, providing information about the effect of money earned on search result rankings on or before the search results page and making certain adjustments to how discounts and statements concerning popularity or availability are shown to consumers. The CMA has stated that it expects all participants in the online travel market to adhere to the same standards, regardless of whether they formally signed the commitments. As a result of additional inquiries from other NCAs in the European Union, Booking.com has made similar commitments with the Consumer Protection Cooperation Network that became applicable in the European Union in June 2020. In the future, it is possible other jurisdictions could engage Booking.com in discussions to implement similar changes to its business in those countries. The Company is unable to predict what, if any, effect these commitments and any future similar commitments will have on its business, industry practices or online commerce more generally. To the extent that any other investigations or inquiries result in additional commitments, fines, damages or other remedies, the Company's business, financial condition and results of operations could be harmed. The Company is involved in litigation in Israel claiming that it has violated Israeli consumer protection and competition laws. One such lawsuit alleges that the Company violated Israeli consumer protection laws by failing to properly display Israeli local taxes in the total prices shown to Israeli residents on its platform. Another lawsuit claims that the Company's parity contractual terms with partners violate Israeli competition laws because they are anti-competitive. A third lawsuit claims Israeli consumer protection laws prohibit the Company from facilitating non-refundable bookings to Israeli residents. Each of the plaintiffs in these matters is requesting certification of a class and the Company is defending against class certification. If the court were to grant class certification for any of these matters and if the plaintiffs were successful on the merits of the claims, the Company could be required to pay damages. However, it is not reasonably possible to estimate the amount of such damages because the likelihood of class certification and the success of the merits of these cases are both too speculative at this stage in the litigation and also because a reasonable assessment of the size of any potential class is not possible at this time. The Company is unable to predict how any current or future investigations or litigation may be resolved or the long-term impact of any such resolution on its business. For example, competition and consumer-law-related investigations, legislation or issues have and could in the future result in private litigation. More immediate results could include, among other things, the imposition of fines, commitments to change certain business practices or reputational damage, any of which could harm the Company's business, results of operations, brands or competitive position. Tax Matters French tax authorities conducted audits of Booking.com for the years 2003 through 2012 and 2013 through 2015 and currently are conducting an audit for the years 2016 through 2018. They are asserting that Booking.com has a permanent establishment in France and are seeking to recover what they claim are unpaid income and value-added taxes. In December 2015, the French tax authorities issued Booking.com assessments related to tax years 2006 through 2012 for approximately 356 million Euros, the majority of which represents penalties and interest. As a result of a formal demand from the French tax authorities for payment of the amounts assessed for the years 2006 through 2012, in January 2019, the Company paid the assessments of approximately 356 million Euros ($403 million) in order to preserve its right to contest those assessments in court. The payment, which is included in "Other assets, net" in the Consolidated Balance Sheets at June 30, 2020 and December 31, 2019, does not constitute an admission that the Company owes the taxes and will be refunded (with interest) to the Company to the extent the Company prevails. If the Company is unable to resolve the matter with the French tax authorities, the Company plans to challenge the assessments in the French courts. In December 2019, the French tax authorities issued an additional assessment of 70 million Euros ($79 million), including interest and penalties, for the 2013 year asserting that Booking.com has taxable income in France attributable to a permanent establishment in France. Furthermore, the French tax authorities issued assessments totaling 39 million Euros ($44 million), including interest and penalties, for certain tax years between 2011 and 2015 on Booking.com's French subsidiary asserting that the subsidiary did not receive sufficient compensation for the services it rendered to Booking.com in the Netherlands. The Company has not recorded a liability in connection with any of the French tax assessments as the Company believes that Booking.com has been, and continues to be, in compliance with French tax law, and the Company is contesting the assessments. Additional assessments could result when the French tax authorities complete the outstanding audits. Italian authorities are reviewing Booking.com's activities for the years 2011 through 2018. They are reviewing whether Booking.com has a permanent establishment in Italy and Booking.com's transfer pricing policies in Italy. The Company is cooperating with the investigation but intends to contest any allegation that Booking.com has a permanent establishment in Italy or that its transfer pricing policies are inappropriate. In December 2018 and 2019, the Italian tax authorities issued assessments on Booking.com's Italian subsidiary for approximately 48 million Euros ($53 million) for the 2013 tax year and 58 million Euros ($65 million) for the 2014 tax year, respectively, asserting that its transfer pricing policies were inadequate. The Company has not recorded a liability in connection with these assessments. The Company believes that Booking.com has been, and continues to be, in compliance with Italian tax law. The Company paid 10 million Euros ($11 million) in December 2019 as a partial prepayment of the 2013 assessment to avoid any collection enforcement from the Italian tax authorities pending the appeal phase of this case. The payment, which is included in "Other assets, net" in the Consolidated Balance Sheets at June 30, 2020 and December 31, 2019, does not constitute an admission that the Company owes the taxes and will be refunded (with interest) to the Company to the extent the Company prevails. It is unclear what further actions, if any, the Italian authorities will take. Such actions could include closing the investigation, assessing Booking.com additional taxes, and/or imposing interest, fines and penalties. In addition, Turkish tax authorities have asserted that Booking.com has a permanent establishment in Turkey and have issued tax assessments for the years 2012 through 2017 for approximately 544 million Turkish Lira ($79 million), including interest and penalties. The Company believes that Booking.com has been, and continues to be, in compliance with Turkish tax law, and the Company is contesting these assessments. The Company has not recorded a liability in connection with these assessments. As a result of an internal review of tax policies and positions at one of the Company's smaller subsidiaries, the Company identified two issues related to the application of certain non-income-based tax laws to that subsidiary's business in 2018. At June 30, 2020 and December 31, 2019, the Company had $75 million and $67 million, respectively, accrued related to these travel transaction taxes based on the Company's estimate of the probable travel transaction tax owed for the prior periods, including interest and penalties, as applicable. The related expenses are included in "General and administrative" expense in the Unaudited Consolidated Statements of Operations. The Company currently estimates that the reasonably possible loss related to these matters in excess of the amount accrued is approximately $25 million. The Company's internal review is ongoing, and, to the extent the Company determines that the probable taxes owed related to these matters e xceed what has already been accrued or new issues are identified during this review, the Company may need to accrue additional amounts, which could adversely affect the Company’s business, results of operations, financial condition and cash flows. From time to time, the Company is involved in other tax-related audits, investigations or proceedings, which could relate to income taxes, value-added taxes, sales taxes, employment taxes, etc. For example, the Company is subject to legal proceedings in the United States related to travel transaction taxes (e.g., hotel occupancy taxes, sales taxes, etc.). Any taxes or other assessments in excess of the Company's current tax provisions, whether in connection with the foregoing or otherwise (including the resolution of any tax proceedings), could have a materially adverse impact on the Company's results of operations, cash flows and financial condition. Other Matters Beginning in 2014, Booking.com received several letters from the Netherlands Pension Fund for the Travel Industry (Reiswerk) (“BPF”) claiming that Booking.com is required to participate in the mandatory pension scheme of the BPF with retroactive effect to 1999, which has a higher contribution rate than the pension scheme in which Booking.com is currently participating. BPF instituted legal proceedings against Booking.com and in 2016 the District Court of Amsterdam rejected all of BPF’s claims. BPF appealed the decision to the Court of Appeal, and, in May 2019, the Court of Appeal also rejected all of BPF’s claims. BPF has appealed to the Netherlands Supreme Court. The Company expects the Supreme Court to rule in early 2021. The Company believes that Booking.com is in compliance with its pension obligations. The Company has not recorded a liability in connection with a potential adverse outcome to this litigation. However, if Booking.com were to lose and all of BPF’s claims were to be accepted (including retroactivity to 1999), the Company estimates that as of June 30, 2020 the maximum loss, not including any potential interest or penalties, would be approximately $245 million. Such estimated potential loss increases as Booking.com continues not to contribute to the BPF and depends on Booking.com’s applicable employee compensation after June 30, 2020. The Company accrues for certain legal contingencies where it is probable that a loss has been incurred and the amount can be reasonably estimated. Such accrued amounts are not material to the Company's balance sheets and provisions recorded have not been material to the Company's results of operations or cash flows. From time to time, the Company has been, and expects to continue to be, subject to legal proceedings and claims in the ordinary course of business, including claims of alleged infringement of third-party intellectual property rights. Such claims, even if not meritorious, could result in the expenditure of significant financial and managerial resources, divert management's attention from the Company's business objectives and adversely affect the Company's business, results of operations, financial condition and cash flows. Building Construction In September 2016, the Company signed a turnkey agreement to construct an office building for Booking.com’s future headquarters in the Netherlands. Upon signing this agreement, the Company paid 43 million Euros ($48 million) for the acquired land-use rights, which was included in "Operating lease assets" in the Consolidated Balance Sheets. In addition, since signing the turnkey agreement the Company has made several progress payments principally related to the construction of the building, which are included in "Property and equipment, net" in the Consolidated Balance Sheets. As of June 30, 2020, the Company has paid 178 million Euros ($204 million) and had a remaining obligation of 84 million Euros ($94 million) at June 30, 2020, related to the turnkey agreement. The Company's contractual obligation was reduced by 9 million Euros ($10 million) during the three months ended June 30, 2020. The remaining obligation will be paid through mid-2022, when the Company anticipates construction will be complete. In addition to the turnkey agreement, the Company has a remaining obligation at June 30, 2020 to pay 71 million Euros ($80 million) over the remaining initial term of the acquired land lease, which expires in 2065. The Company has made and will continue to make additional capital expenditures to fit out and furnish the office space. Other Contractual Obligations

OTHER (Notes)

OTHER (Notes)	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
OTHER	OTHER Restricted Cash and Cash Equivalents Restricted cash and cash equivalents at June 30, 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): June 30, December 31, (Unaudited) As included in the Consolidated Balance Sheets: Cash and cash equivalents $ 10,404 $ 6,312 Restricted cash and cash equivalents included in "Prepaid expenses and other current assets, net" 19 20 Total cash and cash equivalents and restricted cash and cash equivalents as shown in the Unaudited Consolidated Statements of Cash Flows $ 10,423 $ 6,332 Income Taxes Prepayment and Refund In the first quarter of 2020, the Company made a prepayment of the Netherlands income taxes of 660 million Euros ($717 million) to earn prepayment discounts. The Company requested a refund of this amount from the Dutch tax authorities and it was received in April 2020. Restructuring and other Exit Costs In response to the reduction in the Company's business volumes as a result of the impact of the COVID-19 pandemic (see Note 1), the Company has taken actions to reduce the size of its workforce to optimize efficiency. During the three months ended June 30, 2020, agoda, KAYAK and OpenTable initiated restructuring actions, as part of their respective restructuring plans, resulting in a reduction in the workforce of approximately 1,700 employees. In addition, in July 2020, the Company initiated restructuring actions at priceline. The total pretax charges related to these restructuring actions initiated during the three months ended June 30, 2020, estimated at approximately $34 million, are primarily cash-based and consist of employee severance and other one-time termination benefits, and other costs. The Company expects the payments for these restructuring costs to be substantially completed by December 2020. During the three and six months ended June 30, 2020, the Company recorded expenses of $34 million, which are included in “Restructuring and other exit costs” in the Unaudited Consolidated Statements of Operations and made cash payments of $25 million. At June 30, 2020, restructuring liabilities of $7 million are included in "Accrued expenses and other current liabilities" in the Consolidated Balance Sheets. On August 4, 2020, the Company announced its intention to reduce Booking.com's global workforce by up to approximately 25% as a result of the impact of the COVID-19 pandemic on Booking.com and the travel industry. Booking.com is in the process of consulting with its works councils, employee representatives and other relevant organizations where applicable (including in the Netherlands) regarding the intended reduction in force and related cost reduction and restructuring actions. As the Company consults with works councils, employee representatives and other organizations regarding its intentions, the Company expects to develop more clarity on the timing, the number of affected employees, financial impact and other aspects of the contemplated cost reduction actions. The Company expects to finalize its plans and make relevant announcements to employees on a country-by-country basis, with the first countries starting in September 2020, and expects to complete all such announcements by the end of 2020. Government Grants and other Assistance Certain governments have passed or are considering modifying legislation to help businesses during the COVID-19 pandemic through loans, wage subsidies, tax relief or other financial aid, and some of these governments have extended or are considering extending these programs. The Company has participated in several of these programs, including the Netherlands' wage subsidy program, the United Kingdom's job retention scheme and certain other jurisdictions' programs. In addition, in certain countries, such as Singapore and China, the Company is also participating in programs where the government assistance is in the form of wage subsidies and reductions in wage-related employer taxes paid by the Company. During the three and six months ended June 30, 2020, the Company recognized government grants and other assistance benefit of $100 million, of which $84 million has been received as of June 30, 2020. The government grants and other assistance is recorded as a reduction of "Personnel" expense in the Unaudited Consolidated Statements of Operations. At June 30, 2020, the Company has recorded a receivable of $16 million, included in “Prepaid expenses and other current assets, net” in the Consolidated Balance Sheets, for payments expected to be received for the programs where it has met the qualifying requirements and it is probable that payment will be received. These payments are expected to be received in 2020.

BASIS OF PRESENTATION (Policies

BASIS OF PRESENTATION (Policies)	6 Months Ended
	Jun. 30, 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 Consolidated Statements of Operations for the three and six months ended June 30, 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 additional 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 expected 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 additional information related to allowance for expected credit losses on accounts receivable and other financial assets and Note 5 for additional information related to investments in available-for-sale debt securities.
Other Recent Accounting Pronouncement(s)	Other Recent Accounting Pronouncement Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity In August 2020, the FASB issued a new accounting update relating to convertible instruments and contracts in an entity’s own equity. For convertible instruments, the accounting update reduces the number of accounting models for convertible debt instruments and convertible preferred stock. Limiting the accounting models results in fewer embedded conversion features being separately recognized from the host contract as compared with current GAAP. The accounting update amends the guidance for the derivatives scope exception for contracts in an entity’s own equity to reduce form-over-substance-based accounting conclusions. The accounting update also simplifies the diluted earnings per share calculation in certain areas. For public business entities, the update is effective for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years. Early adoption is permitted for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years. The Company is currently evaluating the impact to its Consolidated Financial Statements of adopting this update. 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. For public business entities, this update is effective for fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. Early adoption is permitted. The amendment related to franchise taxes that are partially based on income should be applied on either a retrospective basis for all periods presented or a modified retrospective basis through a cumulative-effect adjustment to retained earnings as of the beginning of the fiscal year of adoption. All other

STOCK-BASED EMPLOYEE COMPENSA_2

STOCK-BASED EMPLOYEE COMPENSATION (Policies)	6 Months Ended
	Jun. 30, 2020
Share-based Payment Arrangement [Abstract]
Share-based Payment Arrangement	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 is determined using the Black-Scholes model. Performance share units and restricted stock units are payable in shares of the Company's common stock upon vesting. The Company issues shares of its common stock upon the exercise of stock options. 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.

NET INCOME PER SHARE (Policies)

NET INCOME PER SHARE (Policies)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Earnings Per Share, Policy	The Company computes basic net income (loss) per share by dividing net income (loss) 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

INVESTMENTS (Policies)

INVESTMENTS (Policies)	6 Months Ended
	Jun. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Investment, Policy	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. 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 expected 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 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

FAIR VALUE MEASUREMENTS (Polici

FAIR VALUE MEASUREMENTS (Policies)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurement, Policy	Investments See Note 5 for additional 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

ACCOUNTS RECEIVABLE AND OTHER_2

ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS (Policies)	6 Months Ended
	Jun. 30, 2020
Receivables [Abstract]
Allowance for 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 expected 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.

INTANGIBLE ASSETS AND GOODWIL_2

INTANGIBLE ASSETS AND GOODWILL (Policies)	6 Months Ended
	Jun. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets, Goodwill, Policy	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.
Goodwill and Intangible Assets, Intangible Assets, Policy	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.

INCOME TAXES (Policies)

INCOME TAXES (Policies)	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income Tax, Policy	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.

REVENUE (Tables)

REVENUE (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 2020 $ 105 $ 444 $ 81 $ 630 2019 (1) 400 2,997 453 3,850 Total revenues for the six months ended June 30, 2020 $ 390 $ 2,121 $ 407 $ 2,918 2019 (1) 766 5,069 852 6,687
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 six months ended June 30, 2020 (in millions): Balance, December 31, 2019 $ 220 Revenues recognized from the beginning deferred revenue balance (147) Cancellations and amendments (61) Payments received from travelers, net of amounts estimated to be payable to travel service providers, and other 137 Balance, June 30, 2020 $ 149

STOCK-BASED EMPLOYEE COMPENSA_3

STOCK-BASED EMPLOYEE COMPENSATION (Tables)	6 Months Ended
	Jun. 30, 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 six months ended June 30, 2020: Restricted Stock Units Shares Weighted-average Grant-date Fair Value Per Share Unvested at December 31, 2019 256,745 $ 1,801 Granted 212,913 $ 1,644 Vested (117,709) $ 1,811 Forfeited (15,636) $ 1,784 Unvested at June 30, 2020 336,313 $ 1,698
Activity of unvested performance share units	The following table summarizes the activity of performance share units for employees during the six months ended June 30, 2020: Performance Share Units Shares Weighted-average Grant-date Fair Value Per Share Unvested at December 31, 2019 216,083 $ 1,835 Vested (81,396) $ 1,740 Performance Shares Adjustment * (50,182) $ 1,944 Forfeited (4,547) $ 1,840 Unvested at June 30, 2020 79,958 $ 1,859
Estimated vesting of performance share units granted [Table Text Block]	The following table summarizes the estimated vesting, as of June 30, 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 44,237 35,721 Shares not subject to the achievement of minimum performance thresholds 44,237 35,721 Shares that could be issued if maximum performance thresholds are met 115,310 62,606
Stock option valuation assumptions	The following table summarizes the assumptions used to value option grants granted in the six months ended June 30, 2020 using the Black-Scholes options pricing model: Black-Scholes assumptions Risk-free interest rate 0.56 % Expected term in years 6.4 Expected stock price volatility 33.8 % Expected dividend yield 0 %
Share-based payment arrangement option activity	The following table summarizes the activity for stock options during the six months ended June 30, 2020: Employee Stock Options Number of Shares Weighted-average Aggregate Weighted-average Remaining Contractual Term Balance, December 31, 2019 15,122 $ 484 $ 24 2.6 Granted 163,494 $ 1,411 Exercised (12,884) $ 464 Forfeited (690) $ 1,411 Balance, June 30, 2020 165,042 $ 1,400 $ 32 9.8 Exercisable at June 30, 2020 2,238 $ 616 $ 2 2.5

NET INCOME PER SHARE (Tables)

NET INCOME PER SHARE (Tables)	6 Months Ended
	Jun. 30, 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 income (loss) per share is as follows (in thousands): Three Months Ended Six Months Ended 2020 2019 2020 2019 Weighted-average number of basic common shares outstanding 40,922 43,251 41,007 44,124 Weighted-average dilutive stock options, restricted stock units and performance share units 73 146 — 188 Assumed conversion of convertible senior notes — 204 — 202 Weighted-average number of diluted common and common equivalent shares outstanding 40,995 43,601 41,007 44,514

INVESTMENTS (Tables)

INVESTMENTS (Tables)	6 Months Ended
	Jun. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Investment [Table Text Block]	The following table summarizes, by major security type, the Company's investments at June 30, 2020 (in millions): Cost Gross Gross Carrying Value Long-term investments: Investments in private companies: Debt securities $ 250 $ — $ — $ 250 Equity securities 501 — (100) 401 Other long-term investments: Debt securities: Trip.com Group convertible debt securities 525 — (25) 500 Equity securities 461 1,336 (2) 1,795 Total $ 1,737 $ 1,336 $ (127) $ 2,946 The following table summarizes, by major security type, the Company's investments at December 31, 2019 (in millions): Cost Gross Gross Unrealized Losses/Downward Adjustments 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)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Financial assets and liabilities carried at fair value	Financial assets and liabilities carried at fair value at June 30, 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 fund investments $ 10,089 $ — $ — $ 10,089 Time deposits and certificates of deposit 25 — — 25 Long-term investments: Investments in private companies: Debt securities — — 250 250 Other long-term investments: Trip.com Group convertible debt securities — 500 — 500 Equity securities 1,795 — — 1,795 Derivatives: Foreign currency exchange derivatives — 4 — 4 Total assets at fair value $ 11,909 $ 504 $ 250 $ 12,663 LIABILITIES: Foreign currency exchange derivatives $ — $ 3 $ — $ 3 Nonrecurring fair value measurements Investment in Didi Chuxing (1) $ — $ — $ 400 $ 400 Goodwill of the OpenTable and KAYAK reporting unit (2) — — 1,545 1,545 Total nonrecurring fair value measurements $ — $ — $ 1,945 $ 1,945 (1) At March 31, 2020, the investment in DiDi Chuxing was written down to its estimated fair value of $400 million, resulting in an impairment charge of $100 million (see Note 5). (2) At March 31, 2020, the goodwill of OpenTable and KAYAK reporting unit was written down to its estimated fair value of $1.5 billion, resulting in an impairment charge of $489 million (see Note 8). 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 fund investments $ 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
Fair value and notional amount of derivatives and the effect of foreign currency exchange derivatives	The table below provides estimated fair values and notional amounts of foreign currency exchange derivatives outstanding at June 30, 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. June 30, 2020 December 31, 2019 Estimated fair value of derivative assets $ 4 $ 12 Estimated fair value of derivative liabilities 3 5 Notional amount: Foreign currency purchases 1,050 1,770 Foreign currency sales 636 901 The effect of foreign currency exchange derivatives recorded in "Foreign currency transactions and other" in the Unaudited Consolidated Statements of Operations for the three and six months ended June 30, 2020 and 2019 is as follows (in millions): Three Months Ended Six Months Ended 2020 2019 2020 2019 (Losses) gains on foreign currency exchange derivatives $ (8) $ 8 $ (31) $ (5)

ACCOUNTS RECEIVABLE AND OTHER_3

ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS (Tables)	6 Months Ended
	Jun. 30, 2020
Receivables [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): Six Months Ended 2020 2019 Balance, beginning of year $ 49 $ 51 Provision charged to earnings 241 38 Write-offs and adjustments (11) (40) Currency translation adjustments 3 (1) Balance, end of period $ 282 $ 48

INTANGIBLE ASSETS AND GOODWIL_3

INTANGIBLE ASSETS AND GOODWILL (Tables)	6 Months Ended
	Jun. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill [Table Text Block]	The changes in the balance of goodwill for the six months ended June 30, 2020 consist of the following (in millions): Balance, December 31, 2019 (1) $ 2,913 Impairment (489) Foreign currency translation adjustments (12) Balance, June 30, 2020 (1) $ 2,412 (1) The balance of goodwill as of June 30, 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 June 30, 2020 and December 31, 2019 consist of the following (in millions): June 30, 2020 December 31, 2019 Gross Accumulated Net Gross Accumulated Net Amortization Supply and distribution agreements $ 1,094 $ (498) $ 596 $ 1,100 $ (472) $ 628 3 - 20 years Technology 170 (135) 35 170 (129) 41 2 - 7 years Internet domain names 39 (33) 6 40 (32) 8 5 - 20 years Trade names 1,808 (580) 1,228 1,811 (534) 1,277 4 - 20 years Other intangible assets 2 (2) — 2 (2) — Up to 15 years Total intangible assets $ 3,113 $ (1,248) $ 1,865 $ 3,123 $ (1,169) $ 1,954

DEBT (Tables)

DEBT (Tables)	6 Months Ended
	Jun. 30, 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 outstanding at June 30, 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 4.1% Senior Notes due April 2025 April 2020 4.10 % Semi-annually in April and October 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 4.5% Senior Notes due April 2027 April 2020 4.54 % Semi-annually in April and October 3.55% Senior Notes due March 2028 August 2017 3.56 % Semi-annually in March and September 4.625% Senior Notes due April 2030 April 2020 4.65 % Semi-annually in April and October
Schedule of Debt	Outstanding debt at June 30, 2020 consists of the following (in millions): June 30, 2020 Outstanding Principal Amount Unamortized Debt Carrying Value Current liabilities: 0.9% Convertible Senior Notes due September 2021 $ 1,000 $ (27) $ 973 Long-term debt: 0.8% (€1 Billion) Senior Notes due March 2022 $ 1,123 $ (2) $ 1,121 2.15% (€750 Million) Senior Notes due November 2022 842 (1) 841 2.75% Senior Notes due March 2023 500 (2) 498 2.375% (€1 Billion) Senior Notes due September 2024 1,123 (8) 1,115 3.65% Senior Notes due March 2025 500 (2) 498 4.1% Senior Notes due April 2025 1,000 (5) 995 0.75% Convertible Senior Notes due May 2025 863 (141) 722 3.6% Senior Notes due June 2026 1,000 (5) 995 1.8% (€1 Billion) Senior Notes due March 2027 1,123 (4) 1,119 4.5% Senior Notes due April 2027 750 (6) 744 3.55% Senior Notes due March 2028 500 (3) 497 4.625% Senior Notes due April 2030 1,500 (12) 1,488 Total long-term debt $ 10,824 $ (191) $ 10,633 Outstanding debt at December 31, 2019 consists of the following (in millions): December 31, 2019 Outstanding Unamortized Debt 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)	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Schedule of Stock Repurchase Activity	The following table summarizes the Company's stock repurchase activities during the three and six months ended June 30, 2020 and 2019 (in millions, except for shares, which are reflected in thousands): Three Months Ended Six Months Ended 2020 2019 2020 2019 Shares Amount Shares Amount Shares Amount Shares Amount Authorized stock repurchase programs — $ — 1,434 $ 2,590 601 $ 1,122 2,982 $ 5,325 General authorization for shares withheld on stock award vesting 2 4 8 16 79 133 79 137 Total 2 $ 4 1,442 $ 2,606 680 $ 1,255 3,061 $ 5,462

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE INCOME (Tables)	6 Months Ended
	Jun. 30, 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 and six months ended June 30, 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) benefit Three Months Ended June 30, 2020 Balance, March 31, 2020 $ (314) $ 58 $ 60 $ (20) $ (216) $ (97) $ (29) $ (126) $ (342) Other Comprehensive Income (Loss) ("OCI") before reclassifications 65 — (43) 10 32 73 (11) 62 94 Amounts reclassified to net income (3) — — — — — — 15 15 15 OCI for the period 65 — (43) 10 32 73 4 77 109 Balance, June 30, 2020 $ (249) $ 58 $ 17 $ (10) $ (184) $ (24) $ (25) $ (49) $ (233) Six Months Ended June 30, 2020 Balance, December 31, 2019 $ (186) $ 54 $ (2) $ (5) $ (139) $ (7) $ (45) $ (52) $ (191) OCI before reclassifications (63) 4 19 (5) (45) (21) 6 (15) (60) Amounts reclassified to net income (3) — — — — — 4 14 18 18 OCI for the period (63) 4 19 (5) (45) (17) 20 3 (42) Balance, June 30, 2020 $ (249) $ 58 $ 17 $ (10) $ (184) $ (24) $ (25) $ (49) $ (233) 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) benefit Three Months Ended June 30, 2019 Balance, March 31, 2019 $ (189) $ 52 $ 3 $ (7) $ (141) $ 53 $ (81) $ (28) $ (169) OCI before reclassifications 10 4 (41) 11 (16) (50) 14 (36) (52) Amounts reclassified to net income (3) — — — — — (10) 1 (9) (9) OCI for the period 10 4 (41) 11 (16) (60) 15 (45) (61) Balance, June 30, 2019 $ (179) $ 56 $ (38) $ 4 $ (157) $ (7) $ (66) $ (73) $ (230) Six Months Ended June 30, 2019 Balance, December 31, 2018 $ (109) $ 41 $ (73) $ 12 $ (129) $ (157) $ (30) $ (187) $ (316) OCI before reclassifications (70) 15 35 (8) (28) 161 (37) 124 96 Amounts reclassified to net income (3) — — — — — (11) 1 (10) (10) OCI for the period (70) 15 35 (8) (28) 150 (36) 114 86 Balance, June 30, 2019 $ (179) $ 56 $ (38) $ 4 $ (157) $ (7) $ (66) $ (73) $ (230) (1) Net investment hedges balance, net of tax, at June 30, 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) gains before tax from sales of investments in debt securities and impairment losses before tax related to debt securities are included in "Foreign currency transactions and other" and the related reclassified tax benefits (expenses) are included in "Income tax 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. For the three and six months ended June 30, 2020, the reclassified tax expenses includes a tax expense of $15 million related to the maturity in May 2020 of the Company's investment of $250 million in Trip.com Group convertible notes (see Note 5).

OTHER (Tables)

OTHER (Tables)	6 Months Ended
	Jun. 30, 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): June 30, December 31, (Unaudited) As included in the Consolidated Balance Sheets: Cash and cash equivalents $ 10,404 $ 6,312 Restricted cash and cash equivalents included in "Prepaid expenses and other current assets, net" 19 20 Total cash and cash equivalents and restricted cash and cash equivalents as shown in the Unaudited Consolidated Statements of Cash Flows $ 10,423 $ 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]
Debt issued	$ 4,100
Cumulative effect of adoption of accounting standards update		$ (3)
Retained Earnings
Organization, Consolidation And Presentation Of Financial Statements [Line Items]
Cumulative effect of adoption of accounting standards update		$ (3)

REVENUE - Disaggregation of rev

REVENUE - Disaggregation of revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 630	$ 3,850	$ 2,918	$ 6,687
Online accommodation reservation services [Member] | Revenue Benchmark [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration risk percentage	86.00%	87.00%	85.00%	86.00%
Other sources of online travel reservation services or advertising and other revenues [Member] | Revenue Benchmark [Member] | Product Concentration Risk [Member] | Maximum
Disaggregation of Revenue [Line Items]
Concentration risk percentage	10.00%	10.00%	10.00%	10.00%
United States
Disaggregation of Revenue [Line Items]
Revenues	$ 105	$ 400	$ 390	$ 766
The Netherlands
Disaggregation of Revenue [Line Items]
Revenues	444	2,997	2,121	5,069
Other
Disaggregation of Revenue [Line Items]
Revenues	$ 81	$ 453	$ 407	$ 852

REVENUE - Deferred Revenue (Det

REVENUE - Deferred Revenue (Details) $ in Millions	6 Months Ended
	Jun. 30, 2020USD ($)
Contract With Customer, Change In Contract Liability, Current [Roll Forward]
Revenues recognized from the beginning deferred revenue balance	$ (147)
Cancellations and amendments	(61)
Payments received from travelers, net of amounts estimated to be payable to travel service providers, and other	137
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, June 30, 2020	$ 149

REVENUE - Other (Details)

REVENUE - Other (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Reduction in revenue for refunds paid or estimated to be payable	$ 63
Accrued Liabilities [Member] | Customer Incentive Programs [Member] | Loyalty Programs [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Contract liabilities, current	67	$ 80
Accrued Liabilities [Member] | Customer Incentive Programs [Member] | Other customer incentive programs [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Contract liabilities, current	$ 30	$ 22

STOCK-BASED EMPLOYEE COMPENSA_4

STOCK-BASED EMPLOYEE COMPENSATION - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 77		$ 79	$ 83	$ 153
Aggregate fair value of performance share units and restricted stock units vested during the period	14			333
Aggregate grant-date fair value	79			79
Performance Share Units | 2018 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incremental fair value as a result of modification of share-based award(s)	11			11
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate grant-date fair values	85			350
Restricted Stock Units and Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized estimated compensation expense, unvested share-based awards	542			$ 542
Total future compensation cost related to unvested share-based awards, expected period of recognition				2 years 2 months 12 days
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized estimated compensation expense, unvested share-based awards	$ 75			$ 75
Total future compensation cost related to unvested share-based awards, expected period of recognition				2 years 8 months 12 days
Adjustment for change in estimated probable outcome at the end of the performance period | Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 73

STOCK-BASED EMPLOYEE COMPENSA_5

STOCK-BASED EMPLOYEE COMPENSATION - Summary of Share-Based Compensation Activity (Details)	6 Months Ended
	Jun. 30, 2020$ / sharesshares
Restricted Stock Units
Share-Based Awards - Shares
Unvested (in shares)	256,745
Granted (in shares)	212,913
Vested (in shares)	(117,709)
Forfeited (in shares)	(15,636)
Unvested (in shares)	336,313
Share-Based Awards - Weighted Average Grant Date Fair Value
Unvested (in dollars per share) | $ / shares	$ 1,801
Granted (in dollars per share) | $ / shares	1,644
Vested (in dollars per share) | $ / shares	1,811
Forfeited (in dollars per share) | $ / shares	1,784
Unvested (in dollars per share) | $ / shares	$ 1,698
Restricted Stock Units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year
Restricted Stock Units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Performance Share Units
Share-Based Awards - Shares
Unvested (in shares)	216,083
Granted (in shares)	0
Vested (in shares)	(81,396)
Performance share units adjustment (in shares)	(50,182)
Forfeited (in shares)	(4,547)
Unvested (in shares)	79,958
Share-Based Awards - Weighted Average Grant Date Fair Value
Unvested (in dollars per share) | $ / shares	$ 1,835
Vested (in dollars per share) | $ / shares	1,740
Performance share units adjustment (in dollars per share) | $ / shares	1,944
Forfeited (in dollars per share) | $ / shares	1,840
Unvested (in dollars per share) | $ / shares	$ 1,859
Performance Share Units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Performance Share Units | 2019 Grants | Shares probable to be issued
Share-Based Awards - Shares
Unvested (in shares)	44,237
Performance Share Units | 2019 Grants | Shares not subject to the achievement of minimum performance thresholds
Share-Based Awards - Shares
Unvested (in shares)	44,237
Performance Share Units | 2019 Grants | Shares that could be issued if maximum performance thresholds are met
Share-Based Awards - Shares
Unvested (in shares)	115,310
Performance Share Units | 2018 Grants | Shares probable to be issued
Share-Based Awards - Shares
Unvested (in shares)	35,721
Performance Share Units | 2018 Grants | Shares not subject to the achievement of minimum performance thresholds
Share-Based Awards - Shares
Unvested (in shares)	35,721
Performance Share Units | 2018 Grants | Shares that could be issued if maximum performance thresholds are met
Share-Based Awards - Shares
Unvested (in shares)	62,606

STOCK-BASED EMPLOYEE COMPENSA_6

STOCK-BASED EMPLOYEE COMPENSATION - Summary of the Assumptions Used to Value Option Grants (Details) - Stock Options	6 Months Ended
	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.56%
Expected term in years	6 years 4 months 24 days
Expected stock price volatility	33.80%
Expected dividend yield	0.00%

STOCK-BASED EMPLOYEE COMPENSA_7

STOCK-BASED EMPLOYEE COMPENSATION - Summary of Stock Option (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Weighted-average Remaining Contractual Term
Weighted-average grant-date fair value per option (in dollars per share)	$ 485
Intrinsic value of options exercised during the period	$ 14	$ 2
Stock Options
Number of Shares
Balance (in shares)	15,122
Granted (in shares)	163,494
Exercised (in shares)	(12,884)
Forfeited (in shares)	(690)
Balance (in shares)	165,042		15,122
Exercisable (in shares)	2,238
Weighted-average Exercise Price
Balance (in dollars per share)	$ 1,400		$ 484
Granted (in dollars per share)	1,411
Exercised (in dollars per share)	464
Forfeited (in dollars per share)	1,411
Exercisable (in dollars per share)	$ 616
Aggregate Intrinsic Value
Balance	$ 32		$ 24
Exercisable	$ 2
Weighted-average Remaining Contractual Term
Balance	9 years 9 months 18 days		2 years 7 months 6 days
Exercisable	2 years 6 months
Stock option term	10 years

NET INCOME PER SHARE (Details)

NET INCOME PER SHARE (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Weighted-average number of basic common shares outstanding (in shares)	40,922,000	43,251,000	41,007,000	44,124,000
Weighted-average dilutive stock options, restricted stock units and performance share units (in shares)	73,000	146,000	0	188,000
Assumed conversion of Convertible Senior Notes (in shares)	0	204,000	0	202,000
Weighted-average number of diluted common and common equivalent shares outstanding (in shares)	40,995,000	43,601,000	41,007,000	44,514,000
Anti-dilutive potential common shares (in shares)	334,000		166,000

INVESTMENTS - Summary of Invest

INVESTMENTS - Summary of Investments by Major Security Type (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Equity security investments in private companies:
Cost		$ 501
Short-term investments:
Carrying Value	$ 0	998
Long-term investments:
Carrying Value	2,946	4,477
Trip.com Group convertible debt securities | Trip.com Group
Debt securities:
Cost	525
Short-term Investments
Short-term investments:
Cost		998
Gross Unrealized Gains /Upward Adjustments		1
Gross Unrealized Losses /Downward Adjustments		(1)
Carrying Value		998
Short-term Investments | International government securities
Debt securities:
Cost		109
Gross Unrealized Gains/Upward Adjustments		0
Gross Unrealized Losses/Downward Adjustments		0
Carrying Value		109
Short-term Investments | U.S. government securities
Debt securities:
Cost		138
Gross Unrealized Gains/Upward Adjustments		0
Gross Unrealized Losses/Downward Adjustments		0
Carrying Value		138
Short-term Investments | Corporate debt securities
Debt securities:
Cost		751
Gross Unrealized Gains/Upward Adjustments		1
Gross Unrealized Losses/Downward Adjustments		(1)
Carrying Value		751
Long-term investments
Long-term investments:
Cost	1,737	3,810
Gross Unrealized Gains /Upward Adjustments	1,336	686
Gross Unrealized Losses /Downward Adjustments	(127)	(19)
Carrying Value	2,946	4,477
Long-term investments | Trip.com Group
Equity security investments with readily determinable fair value:
Cost		655
Carrying Value		726
Long-term investments | International government securities
Debt securities:
Cost		68
Gross Unrealized Gains/Upward Adjustments		0
Gross Unrealized Losses/Downward Adjustments		0
Carrying Value		68
Long-term investments | U.S. government securities
Debt securities:
Cost		136
Gross Unrealized Gains/Upward Adjustments		0
Gross Unrealized Losses/Downward Adjustments		(1)
Carrying Value		135
Long-term investments | Corporate debt securities
Debt securities:
Cost		963
Gross Unrealized Gains/Upward Adjustments		2
Gross Unrealized Losses/Downward Adjustments		(2)
Carrying Value		963
Long-term investments | Debt securities
Debt securities:
Cost	250	250
Gross Unrealized Gains/Upward Adjustments	0	0
Gross Unrealized Losses/Downward Adjustments	0	0
Carrying Value	250	250
Long-term investments | Investment in private company equity securities
Equity security investments in private companies:
Cost	501	501
Gross Unrealized Gains /Upward Adjustments	0	0
Gross Unrealized Losses /Downward Adjustments	(100)	0
Carrying Value	401	501
Long-term investments | Trip.com Group convertible debt securities | Trip.com Group
Debt securities:
Cost	525	775
Gross Unrealized Gains/Upward Adjustments	0	0
Gross Unrealized Losses/Downward Adjustments	(25)	(8)
Carrying Value	500	767
Long-term investments | Equity securities
Equity security investments with readily determinable fair value:
Cost	461	1,117
Gross Unrealized Gains /Upward Adjustments	1,336	684
Gross Unrealized Losses /Downward Adjustments	(2)	(8)
Carrying Value	$ 1,795	$ 1,793

INVESTMENTS - Narrative (Detail

INVESTMENTS - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Proceeds from sale of available-for-sale debt securities				$ 2,200
Net gains/(losses) on marketable equity securities	$ 835		$ 17	528	$ 468
Cost of investment						$ 501
Impairment of investment	0		0	100	0
Trip.com Group
Schedule of Investments [Line Items]
Proceeds from sale of securities				525
Net gains/(losses) on marketable equity securities	17		(147)	(201)	213
Trip.com Group | Trip.com Group convertible debt securities
Schedule of Investments [Line Items]
Amortized cost of available-for-sale debt securities	525			525
Trip.com Group 1% Note Due 2020 [Member] | Trip.com Group convertible debt securities
Schedule of Investments [Line Items]
Amortized cost of available-for-sale debt securities	250			250
Meituan-Dianping [Member]
Schedule of Investments [Line Items]
Fair value of equity securities	1,800			1,800		1,100
Net gains/(losses) on marketable equity securities	813		$ 164	732	$ 255
Payments to acquire investments							$ 450
Long-term Investments | Investment in private company equity securities
Schedule of Investments [Line Items]
Cost of investment	501			501		501
Impairment of investment		$ 100
Investment in equity securities without readily determinable FV	401			401		501
Long-term Investments | Redeemable Convertible Preferred Stock [Member]
Schedule of Investments [Line Items]
Amortized cost of available-for-sale debt securities	250			250
Carrying Value	250			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]
Amortized cost of available-for-sale debt securities	525			525		775
Carrying Value	500			500		767
Long-term Investments | Trip.com Group 1.25% Notes due 2022 | Trip.com Group convertible debt securities
Schedule of Investments [Line Items]
Amortized cost of available-for-sale debt securities								$ 25
Long-term Investments | Didi Chuxing | Investment in private company equity securities
Schedule of Investments [Line Items]
Cost of investment	500			500		500
Investment in equity securities without readily determinable FV	400	400		400
Long-term Investments | Grab | Redeemable Convertible Preferred Stock [Member]
Schedule of Investments [Line Items]
Carrying Value	200			$ 200		$ 200
Debt Securities, Available-for-sale, Unrealized Gain (Loss)	$ 20	$ (20)

FAIR VALUE MEASUREMENTS - Finan

FAIR VALUE MEASUREMENTS - Financial Assets and Liabilities Carried at Fair Value (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of investment	$ 0		$ 0	$ 100	$ 0
Goodwill	2,412			2,412		$ 2,913
Goodwill, Impairment Loss	0		$ 0	(489)	$ 0
OpenTable And KAYAK [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill		$ 1,500
Goodwill, Impairment Loss		(489)		(489)
Investment in private company equity securities | Long-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of investment		100
Recurring Basis
ASSETS:
Assets at fair value	12,663			12,663		10,751
Recurring Basis | Long-term Investments
ASSETS:
Assets at fair value	250			250		250
Recurring Basis | Money market fund investments | Cash Equivalents
ASSETS:
Assets at fair value	10,089			10,089		5,734
Recurring Basis | Time deposits and certificates of deposit | Cash Equivalents
ASSETS:
Assets at fair value	25			25		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						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	1,795			1,795		1,793
Recurring Basis | Trip.com Group | Trip.com Group convertible debt securities | Long-term Investments
ASSETS:
Assets at fair value	500			500		767
Recurring Basis | Not Designated as Hedging Instrument | Foreign Currency Contracts
ASSETS:
Assets at fair value	4			4		12
LIABILITIES:
Liabilities at fair value	3			3		5
Nonrecurring Basis
ASSETS:
Assets at fair value	1,945			1,945
Nonrecurring Basis | Equity securities | Long-term Investments
ASSETS:
Assets at fair value	400	$ 400		400
Nonrecurring Basis | Goodwill
ASSETS:
Assets at fair value	1,545			1,545
Level 1 | Recurring Basis
ASSETS:
Assets at fair value	11,909			11,909		7,556
Level 1 | Recurring Basis | Long-term Investments
ASSETS:
Assets at fair value	0			0		0
Level 1 | Recurring Basis | Money market fund investments | Cash Equivalents
ASSETS:
Assets at fair value	10,089			10,089		5,734
Level 1 | Recurring Basis | Time deposits and certificates of deposit | Cash Equivalents
ASSETS:
Assets at fair value	25			25		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
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	1,795			1,795		1,793
Level 1 | Recurring Basis | Trip.com Group | Trip.com Group convertible debt securities | Long-term Investments
ASSETS:
Assets at fair value	0			0		0
Level 1 | Recurring Basis | Not Designated as Hedging Instrument | Foreign Currency Contracts
ASSETS:
Assets at fair value	0			0		0
LIABILITIES:
Liabilities at fair value	0			0		0
Level 1 | Nonrecurring Basis
ASSETS:
Assets at fair value	0			0
Level 1 | Nonrecurring Basis | Equity securities | Long-term Investments
ASSETS:
Assets at fair value	0			0
Level 1 | Nonrecurring Basis | Goodwill
ASSETS:
Assets at fair value	0			0
Level 2 | Recurring Basis
ASSETS:
Assets at fair value	504			504		2,945
Level 2 | Recurring Basis | Long-term Investments
ASSETS:
Assets at fair value	0			0		0
Level 2 | Recurring Basis | Money market fund investments | Cash Equivalents
ASSETS:
Assets at fair value	0			0		0
Level 2 | Recurring Basis | Time deposits and certificates of deposit | Cash Equivalents
ASSETS:
Assets at fair value	0			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						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		0
Level 2 | Recurring Basis | Trip.com Group | Trip.com Group convertible debt securities | Long-term Investments
ASSETS:
Assets at fair value	500			500		767
Level 2 | Recurring Basis | Not Designated as Hedging Instrument | Foreign Currency Contracts
ASSETS:
Assets at fair value	4			4		12
LIABILITIES:
Liabilities at fair value	3			3		5
Level 2 | Nonrecurring Basis
ASSETS:
Assets at fair value	0			0
Level 2 | Nonrecurring Basis | Equity securities | Long-term Investments
ASSETS:
Assets at fair value	0			0
Level 2 | Nonrecurring Basis | Goodwill
ASSETS:
Assets at fair value	0			0
Level 3 | Recurring Basis
ASSETS:
Assets at fair value	250			250		250
Level 3 | Recurring Basis | Long-term Investments
ASSETS:
Assets at fair value	250			250		250
Level 3 | Recurring Basis | Money market fund investments | Cash Equivalents
ASSETS:
Assets at fair value	0			0		0
Level 3 | Recurring Basis | Time deposits and certificates of deposit | Cash Equivalents
ASSETS:
Assets at fair value	0			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
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		0
Level 3 | Recurring Basis | Trip.com Group | Trip.com Group convertible debt securities | Long-term Investments
ASSETS:
Assets at fair value	0			0		0
Level 3 | Recurring Basis | Not Designated as Hedging Instrument | Foreign Currency Contracts
ASSETS:
Assets at fair value	0			0		0
LIABILITIES:
Liabilities at fair value	0			0		$ 0
Level 3 | Nonrecurring Basis
ASSETS:
Assets at fair value	1,945			1,945
Level 3 | Nonrecurring Basis | Equity securities | Long-term Investments
ASSETS:
Assets at fair value	400			400
Level 3 | Nonrecurring Basis | Goodwill
ASSETS:
Assets at fair value	$ 1,545			$ 1,545

FAIR VALUE MEASUREMENTS - Narra

FAIR VALUE MEASUREMENTS - Narrative (Details) $ in Millions	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)Years	Dec. 31, 2019USD ($)	Dec. 31, 2016USD ($)
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	$ 12,663		$ 10,751
Level 3 | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	250		250
Long-term Investments | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	250		250
Long-term Investments | Level 3 | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	250		250
Long-term Investments | Investment in private company equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in equity securities without readily determinable FV	401		$ 501
Didi Chuxing | Long-term Investments | Investment in private company equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in equity securities without readily determinable FV	400	$ 400
Grab | Long-term Investments | Level 3 | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	$ 200
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]
Amortized cost of available-for-sale debt securities				$ 25
Weighted Average Cost of Capital | Didi Chuxing | 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 | Didi Chuxing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement, inputs (percentages)		14.00%
EBITDA Multiple | Didi Chuxing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement, inputs (number)		13
EBITDA Multiple | Didi Chuxing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement, inputs (number)		15
Volatility | Didi Chuxing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement, inputs (percentages)		60.00%
Volatility | Didi Chuxing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement, inputs (percentages)		70.00%
Expected Term | Didi Chuxing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement, inputs (number) | Years		4

FAIR VALUE MEASUREMENTS - Notio

FAIR VALUE MEASUREMENTS - Notional Amount of Foreign Currency Exchange Derivatives (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Recurring Basis
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Assets at fair value	$ 12,663	$ 10,751
Recurring Basis | Level 2
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Assets at fair value	504	2,945
Recurring Basis | Not Designated as Hedging Instrument | Foreign Currency Contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Assets at fair value	4	12
Liabilities at fair value	3	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	4	12
Liabilities at fair value	3	5
Foreign currency purchases | Not Designated as Hedging Instrument | Foreign Currency Contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	1,050	1,770
Foreign currency sales | Not Designated as Hedging Instrument | Foreign Currency Contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	$ 636	$ 901

FAIR VALUE MEASUREMENTS - Effec

FAIR VALUE MEASUREMENTS - Effect of Foreign Currency Exchange Derivatives (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Fair Value Disclosures [Abstract]
(Losses) gains on foreign currency exchange derivatives	$ (8)	$ 8	$ (31)	$ (5)

ACCOUNTS RECEIVABLE AND OTHER_4

ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, before Allowance for Credit Loss, Current	$ 620		$ 1,200
Other Receivables, Gross, Current	32		110
Prepaid expense, allowance for credit loss	56		6
Accounts Receivable, after Allowance for Credit Loss [Abstract]
Accounts Receivable, Allowance for Credit Loss	49	$ 51
Provision for expected credit losses and chargebacks	241	38
Accounts Receivable, Allowance for Credit Loss, Writeoff	(11)	(40)
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	3	(1)
Accounts Receivable, Allowance for Credit Loss	282	48
Sales and other expenses
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for Other Credit Losses	233	$ 38
COVID-19 [Member] | Merchant revenues
Accounts Receivable, after Allowance for Credit Loss [Abstract]
Provision for expected credit losses and chargebacks	55
Prepaid expenses and other current assets, net
Accounts, Notes, Loans and Financing Receivable [Line Items]
Prepaid Expense	130		232
Prepaid expense, allowance for credit loss	12		6
Other assets, net
Accounts, Notes, Loans and Financing Receivable [Line Items]
Prepaid Expense	80
Prepaid expense, allowance for credit loss	$ 44		$ 0

INTANGIBLE ASSETS AND GOODWIL_4

INTANGIBLE ASSETS AND GOODWILL - Changes in Goodwill (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill			$ 2,913
Goodwill, Impairment Loss	$ 0	$ 0	(489)	$ 0
Goodwill, Foreign Currency Translation Gain (Loss)			(12)
Goodwill	$ 2,412		$ 2,412

INTANGIBLE ASSETS AND GOODWIL_5

INTANGIBLE ASSETS AND GOODWILL (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Finite-lived intangible assets
Impairment of goodwill	$ 0		$ 0	$ 489	$ 0
Goodwill	2,412			2,412		$ 2,913
Goodwill, Impaired, Accumulated Impairment Loss	1,400			1,400		941
Amortization expense	42		$ 44	85	$ 89
Gross  Carrying  Amount	3,113			3,113		3,123
Accumulated Amortization	(1,248)			(1,248)		(1,169)
Net  Carrying  Amount	1,865			1,865		1,954
Supply and distribution agreements
Finite-lived intangible assets
Gross  Carrying  Amount	1,094			1,094		1,100
Accumulated Amortization	(498)			(498)		(472)
Net  Carrying  Amount	596			596		628
Technology
Finite-lived intangible assets
Gross  Carrying  Amount	170			170		170
Accumulated Amortization	(135)			(135)		(129)
Net  Carrying  Amount	35			35		41
Internet domain names
Finite-lived intangible assets
Gross  Carrying  Amount	39			39		40
Accumulated Amortization	(33)			(33)		(32)
Net  Carrying  Amount	6			6		8
Trade Names
Finite-lived intangible assets
Gross  Carrying  Amount	1,808			1,808		1,811
Accumulated Amortization	(580)			(580)		(534)
Net  Carrying  Amount	1,228			1,228		1,277
Other Intangible Assets
Finite-lived intangible assets
Gross  Carrying  Amount	2			2		2
Accumulated Amortization	(2)			(2)		(2)
Net  Carrying  Amount	$ 0			$ 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		$ 489
Goodwill		1,500
OpenTable And KAYAK [Member] | Minimum
Finite-lived intangible assets
Increase (decrease) in the estimated fair value		(410)
OpenTable And KAYAK [Member] | Maximum
Finite-lived intangible assets
Increase (decrease) in the estimated fair value		$ 230

DEBT (Revolving Credit Facility

DEBT (Revolving Credit Facility) (Details) - USD ($)	1 Months Ended		3 Months Ended		6 Months Ended
	Aug. 31, 2019	Jun. 30, 2015	Sep. 30, 2019	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Line of Credit Facility [Line Items]
Long-term Debt					$ 10,633,000,000		$ 7,640,000,000
Letters of credit issued					3,000,000		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						$ 400,000,000
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	$ 2,000,000

DEBT (Outstanding Debt) (Detail

DEBT (Outstanding Debt) (Details)	1 Months Ended		3 Months Ended			6 Months Ended
	Apr. 30, 2020USD ($)Days$ / shares	Aug. 31, 2014USD ($)Days$ / shares	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2015USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020EUR (€)	Dec. 31, 2019USD ($)	Dec. 31, 2019EUR (€)	Aug. 31, 2017	Jun. 30, 2017	May 31, 2016	Nov. 30, 2015	Jun. 30, 2015	Dec. 31, 2014USD ($)	Jun. 30, 2013USD ($)	May 31, 2013USD ($)
Debt Instrument
Outstanding Principal Amount, Long-Term Debt			$ 10,824,000,000			$ 10,824,000,000			$ 7,711,000,000
Unamortized Debt Discount and Debt Issuance Cost			(191,000,000)			(191,000,000)			(71,000,000)
Long-term Debt			10,633,000,000			10,633,000,000			7,640,000,000
Description of Senior Notes
Debt financing costs paid						38,000,000	$ 0
Bank Overdrafts			$ 56,000,000			56,000,000
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%
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	2,000,000
PaymentsRelatedToConversionOfSeniorNotes						1,000,000,000
Debt Conversion Converted Instrument Cash						$ 245,000,000
0.9% Convertible Senior Notes due September 2021
Debt Instrument
Outstanding Principal Amount, Long-Term Debt									1,000,000,000
Unamortized Debt Discount and Debt Issuance Cost									(39,000,000)
Long-term Debt									$ 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%	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			$ 1,123,000,000			$ 1,123,000,000			$ 1,123,000,000
Unamortized Debt Discount and Debt Issuance Cost			(2,000,000)			(2,000,000)			(3,000,000)
Long-term Debt			$ 1,121,000,000			$ 1,121,000,000			$ 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%	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			$ 842,000,000			$ 842,000,000			$ 842,000,000
Unamortized Debt Discount and Debt Issuance Cost			(1,000,000)			(1,000,000)			(3,000,000)
Long-term Debt			$ 841,000,000			$ 841,000,000			$ 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%	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			$ 500,000,000
Unamortized Debt Discount and Debt Issuance Cost			(2,000,000)			(2,000,000)			(2,000,000)
Long-term Debt			$ 498,000,000			$ 498,000,000			$ 498,000,000
Description of Senior Notes
Interest rate on long-term debt			2.75%			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			$ 1,123,000,000			$ 1,123,000,000			$ 1,123,000,000
Unamortized Debt Discount and Debt Issuance Cost			(8,000,000)			(8,000,000)			(9,000,000)
Long-term Debt			$ 1,115,000,000			$ 1,115,000,000			$ 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%	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			$ 500,000,000
Unamortized Debt Discount and Debt Issuance Cost			(2,000,000)			(2,000,000)			(2,000,000)
Long-term Debt			$ 498,000,000			$ 498,000,000			$ 498,000,000
Description of Senior Notes
Interest rate on long-term debt			3.65%			3.65%		3.65%	3.65%	3.65%
Effective interest rate at debt origination or modification															3.68%
3.65% Senior Notes due March 2025
Description of Senior Notes
Effective interest rate at debt origination or modification	4.10%
Debt discount related to convertible notes, net of tax	$ 100,000,000
Debt discount related to convertible notes, before tax	130,000,000
3.6% Senior Notes due June 2026
Debt Instrument
Outstanding Principal Amount, Long-Term Debt			$ 1,000,000,000			$ 1,000,000,000			$ 1,000,000,000
Unamortized Debt Discount and Debt Issuance Cost			(5,000,000)			(5,000,000)			(5,000,000)
Long-term Debt			$ 995,000,000			$ 995,000,000			$ 995,000,000
Description of Senior Notes
Interest rate on long-term debt			3.60%			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			$ 1,123,000,000			$ 1,123,000,000			$ 1,123,000,000
Unamortized Debt Discount and Debt Issuance Cost			(4,000,000)			(4,000,000)			(5,000,000)
Long-term Debt			$ 1,119,000,000			$ 1,119,000,000			$ 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%	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			$ 500,000,000
Unamortized Debt Discount and Debt Issuance Cost			(3,000,000)			(3,000,000)			(3,000,000)
Long-term Debt			$ 497,000,000			$ 497,000,000			$ 497,000,000
Description of Senior Notes
Interest rate on long-term debt			3.55%			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			$ 21,000,000	16,000,000		$ 36,000,000	31,000,000
Amortization of debt discount included in interest expense			15,000,000	12,000,000		27,000,000	24,000,000
Coupon Interest expense			$ 4,000,000	$ 3,000,000		$ 7,000,000	$ 6,000,000
Debt, weighted average interest rate			3.20%	3.20%		3.30%	3.20%
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%
Debt Issuance Costs, Gross	$ 19,000,000
Other Long-term Debt
Debt Instrument
Long-term Debt			$ 9,900,000,000			$ 9,900,000,000			$ 6,700,000,000
Description of Senior Notes
Interest expense related to debt			72,000,000	$ 41,000,000		114,000,000	$ 83,000,000
Coupon Interest expense			70,000,000	$ 40,000,000		110,000,000	$ 80,000,000
4.5% Senior Convertible Notes Due April 2027
Description of Senior Notes
Effective interest rate at debt origination or modification	4.54%
4.625% Senior Convertible Notes Due April 2030
Description of Senior Notes
Effective interest rate at debt origination or modification	4.65%
4.1% Senior Notes due April 2025 [Member]
Debt Instrument
Outstanding Principal Amount, Long-Term Debt	$ 1,000,000,000		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	4.10%		4.10%			4.10%		4.10%
Effective interest rate at debt origination or modification	4.10%
0.75% Convertible Senior Notes due May 2025 [Member]
Debt Instrument
Outstanding Principal Amount, Long-Term Debt			$ 863,000,000			$ 863,000,000
Unamortized Debt Discount and Debt Issuance Cost			(141,000,000)			(141,000,000)
Long-term Debt			$ 722,000,000			$ 722,000,000
Description of Senior Notes
Interest rate on long-term debt			0.75%			0.75%		0.75%
4.5% Senior Notes Due April 2027 [Member]
Debt Instrument
Outstanding Principal Amount, Long-Term Debt	$ 750,000,000		$ 750,000,000			$ 750,000,000
Unamortized Debt Discount and Debt Issuance Cost			(6,000,000)			(6,000,000)
Long-term Debt			$ 744,000,000			$ 744,000,000
Description of Senior Notes
Interest rate on long-term debt	4.50%		4.50%			4.50%		4.50%
4.625% Senior Notes Due April 2030 [Member]
Debt Instrument
Outstanding Principal Amount, Long-Term Debt	$ 1,500,000,000		$ 1,500,000,000			$ 1,500,000,000
Unamortized Debt Discount and Debt Issuance Cost			(12,000,000)			(12,000,000)
Long-term Debt			$ 1,488,000,000			$ 1,488,000,000
Description of Senior Notes
Interest rate on long-term debt	4.625%		4.625%			4.625%		4.625%
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
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
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
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	$ 235,000,000
Level 2
Description of Senior Notes
Estimated market value of outstanding debt			$ 13,000,000,000			$ 13,000,000,000			9,800,000,000
Designated as Hedging Instrument | Minimum | Euro-Denominated Debt
Description of Senior Notes
Notional amount of nonderivative instruments						1,800,000,000
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
Unamortized Debt Discount and Debt Issuance Cost									(12,000,000)
Carrying Value, Short-term debt									988,000,000
Short-term Debt [Member] | 0.9% Convertible Senior Notes due September 2021
Debt Instrument
Outstanding Principal Amount, Short-Term Debt			1,000,000,000			1,000,000,000
Unamortized Debt Discount and Debt Issuance Cost			(27,000,000)			(27,000,000)
Carrying Value, Short-term debt			973,000,000			973,000,000
Recurring Basis
Debt Instrument
Debt Securities, Available-for-sale, Amortized Cost			12,663,000,000			12,663,000,000			10,751,000,000
Recurring Basis | Level 3
Debt Instrument
Debt Securities, Available-for-sale, Amortized Cost			250,000,000			250,000,000			250,000,000
Recurring Basis | Level 2
Debt Instrument
Debt Securities, Available-for-sale, Amortized Cost			504,000,000			504,000,000			2,945,000,000
Long-term Investments | Recurring Basis
Debt Instrument
Debt Securities, Available-for-sale, Amortized Cost			250,000,000			250,000,000			250,000,000
Long-term Investments | Recurring Basis | Level 3
Debt Instrument
Debt Securities, Available-for-sale, Amortized Cost			250,000,000			250,000,000			250,000,000
Long-term Investments | Recurring Basis | Level 2
Debt Instrument
Debt Securities, Available-for-sale, Amortized Cost			0			0			$ 0
Redeemable Convertible Preferred Stock [Member] | Long-term Investments
Description of Senior Notes
Carrying Value			$ 250,000,000			$ 250,000,000

TREASURY STOCK (Details)

TREASURY STOCK (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Dec. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock through authorized stock repurchase programs (in shares)		2,000	1,442,000	680,000	3,061,000
Repurchase of common stock through authorized stock repurchase programs		$ 4,000,000	$ 2,606,000,000	$ 1,255,000,000	$ 5,462,000,000
Repurchase of common stock through general authorization for shares withheld on stock award vesting (in shares)		2,000	8,000	79,000	79,000
Repurchase of common stock through general authorization for shares withheld on stock award vesting		$ 4,000,000	$ 16,000,000	$ 133,000,000	$ 137,000,000
Treasury stock repurchased but unsettled by period end, amount	$ 40,000,000
Payments related to tax withholding for share-based compensation				$ 132,000,000	136,000,000
Treasury stock, shares (in shares)	21,762,070	22,442,328		22,442,328
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		$ 10,400,000,000
Amount of common stock repurchases authorized			$ 15,000,000,000		$ 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)		0	1,434,000	601,000	2,982,000
Repurchase of common stock through authorized stock repurchase programs		$ 0	$ 2,590,000,000	$ 1,122,000,000	$ 5,325,000,000

INCOME TAXES (Details)

INCOME TAXES (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Tax Contingency [Line Items]
Effective income tax rate reconciliation, percent	41.40%	18.90%	(12.40%)	19.80%
Statutory federal rate			21.00%	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		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	$ 3,999	$ 5,307	$ 3,999	$ 5,307	$ 3,831	$ 5,933	$ 6,915	$ 8,785
OCI, before Reclassifications, Net of Tax, Attributable to Parent	94	(52)	(60)	96
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent	(15)	9	(18)	(10)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	109	(61)	(42)	86
Trip.com Group convertible debt securities | Trip.com Group 1% Note Due 2020 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortized cost of available-for-sale debt securities	250		250
Accumulated Foreign Currency Adjustment Attributable To Parent, Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity, before tax	(249)	(179)	(249)	(179)	(314)	(186)	(189)	(109)
AOCI Tax, Attributable to Parent	58	56	58	56	58	54	52	41
OCI, before Reclassifications, before Tax, Attributable to Parent	65	10	(63)	(70)
Other Comprehensive Income (Loss) before Reclassifications, Tax	0	4	4	15
Reclassification from AOCI, Current Period, before Tax, Attributable to Parent	0	0	0	0
Reclassification from AOCI, Current Period, Tax	0	0	0	0
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent	65	10	(63)	(70)
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	0	4	4	15
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	(184)	(157)	(184)	(157)	(216)	(139)	(141)	(129)
OCI, before Reclassifications, Net of Tax, Attributable to Parent	32	(16)	(45)	(28)
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent	0	0	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	32	(16)	(45)	(28)
Foreign currency translation adjustments | Net Investment Hedging | Foreign Currency Forward
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	(35)	(35)	(35)	(35)		(35)		(35)
Stockholders' equity, before tax	(53)	(53)	(53)	(53)		(53)		(53)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	(233)	(230)	(233)	(230)	(342)	(191)	(169)	(316)
Accumulated Net Investment Gain (Loss) Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	(49)	(73)	(49)	(73)	(126)	(52)	(28)	(187)
Stockholders' equity, before tax	(24)	(7)	(24)	(7)	(97)	(7)	53	(157)
AOCI Tax, Attributable to Parent	(25)	(66)	(25)	(66)	(29)	(45)	(81)	(30)
OCI, before Reclassifications, before Tax, Attributable to Parent	73	(50)	(21)	161
Other Comprehensive Income (Loss) before Reclassifications, Tax	(11)	14	6	(37)
OCI, before Reclassifications, Net of Tax, Attributable to Parent	62	(36)	(15)	124
Reclassification from AOCI, Current Period, before Tax, Attributable to Parent	0	(10)	4	(11)
Reclassification from AOCI, Current Period, Tax	15	1	14	1
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent	(15)	9	(18)	(10)
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent	73	(60)	(17)	150
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	4	15	20	(36)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	77	(45)	3	114
Accumulated Net Investment Gain (Loss) Attributable to Parent | Trip.com Group convertible debt securities | Trip.com Group 1% Note Due 2020 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, Current Period, Tax	15
Accumulated Foreign Currency Adjustment Attributable To Parent, Net Investment Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity, before tax	17	(38)	17	(38)	60	(2)	3	(73)
AOCI Tax, Attributable to Parent	(10)	4	(10)	4	$ (20)	$ (5)	$ (7)	$ 12
OCI, before Reclassifications, before Tax, Attributable to Parent	(43)	(41)	19	35
Other Comprehensive Income (Loss) before Reclassifications, Tax	10	11	(5)	(8)
Reclassification from AOCI, Current Period, before Tax, Attributable to Parent	0	0	0	0
Reclassification from AOCI, Current Period, Tax	0	0	0	0
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent	(43)	(41)	19	35
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	$ 10	$ 11	$ (5)	$ (8)

COMMITMENTS AND CONTINGENCIES_2

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

1 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

Dec. 31, 2019EUR (€)

Dec. 31, 2019USD ($)

Jan. 31, 2019EUR (€)

Jan. 31, 2019USD ($)

Sep. 30, 2016EUR (€)

Sep. 30, 2016USD ($)

Dec. 31, 2015EUR (€)

Jun. 30, 2020EUR (€)

Jun. 30, 2020USD ($)

Jun. 30, 2020EUR (€)

Jun. 30, 2020USD ($)

Dec. 31, 2019USD ($)

Dec. 31, 2019TRY (₺)

Dec. 31, 2018EUR (€)ft²

Dec. 31, 2018USD ($)ft²

Jun. 30, 2020USD ($)

Jun. 30, 2020GBP (£)

Booking.com | Headquarters

Commitments and Contingencies

Acquisition of land use rights

€ 43

$ 48

Contractual obligation

€ 84

€ 84

$ 94

Payment Of Contractual Obligation

178

$ 204

Other Increases/(Decreases) in Amounts Owed for Contractual Obligations

9

$ 10

Booking.com | Headquarters | Ground Lease

Commitments and Contingencies

Contractual obligation

€ 71

€ 71

80

French Tax Audit

Commitments and Contingencies

Assessed taxes including interest and penalties

€ 70

$ 79

€ 356

Payment required to appeal a litigation matter

€ 356

$ 403

Assessment, transfer taxes [Member]

Commitments and Contingencies

Assessed taxes including interest and penalties

39

44

Taxes Owed For Prior Periods

Commitments and Contingencies

Loss contingency accrual

67

$ 67

75

Estimated reasonably possible loss in excess of amount accrued

25

Italian Tax Audit

Commitments and Contingencies

Assessed taxes including interest and penalties

58

65

€ 48

$ 53

Payment required to appeal a litigation matter

€ 10

$ 11

Turkish Tax Audit

Commitments and Contingencies

Assessed taxes including interest and penalties

$ 79

₺ 544

Pension-related litigation [Member]

Commitments and Contingencies

Estimated reasonably possible loss in excess of amount accrued

$ 245

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

13 years

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

Commitments and Contingencies

Contractual obligation

$ 80

£ 65

OTHER - Reconciliation of Cash

OTHER - Reconciliation of Cash and Cash Equivalents and Restricted Cash and Cash Equivalents (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 10,404	$ 6,312
Restricted cash and cash equivalents included in "Prepaid expenses and other current assets, net"	19	20
Total cash and cash equivalents and restricted cash and cash equivalents as shown in the Unaudited Consolidated Statements of Cash Flows	$ 10,423	$ 6,332	$ 5,276	$ 2,645

OTHER - Narrative (Details)

OTHER - Narrative (Details) € in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020USD ($)employee	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Aug. 04, 2020	Mar. 31, 2020USD ($)	Mar. 31, 2020EUR (€)
Restructuring Cost and Reserve [Line Items]
Number of employees terminated | employee	1,700
Restructuring and other exit costs	$ 34
Restructuring and other exit costs	34	$ 0	$ 34	$ 0
Payments for Restructuring			25
Restructuring Reserve	7		7
Government grants and other assistance benefit recognized	100		100
Proceeds from Government Assistance	84		84
Grants Receivable	$ 16		$ 16
Tax and Customs Administration, Netherlands
Restructuring Cost and Reserve [Line Items]
Prepaid taxes						$ 717	€ 660
Forecast [Member] | Booking.com | Subsequent Event [Member]
Restructuring Cost and Reserve [Line Items]
Workforce Subject to Termination due to Restructuring					25.00%