Booking (BKNG) 10-Q3 Nov 212021 Q3 Quarterly reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2021	Oct. 27, 2021
Entity Information [Line Items]
Document Type	10-Q
Document Fiscal Period Focus	Q3
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Amendment Flag	false
Document Fiscal Year Focus	2021
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		41,063,485
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
0.100% Senior Notes Due 2025
Entity Information [Line Items]
Title of 12(b) Security	0.100% Senior Notes Due 2025
Trading Symbol	BKNG 25
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
0.500% Senior Notes Due 2028
Entity Information [Line Items]
Title of 12(b) Security	0.500% Senior Notes Due 2028
Trading Symbol	BKNG 28
Security Exchange Name	NASDAQ

UNAUDITED CONSOLIDATED BALANCE

UNAUDITED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 11,643	$ 10,562
Short-term investments (Available-for-sale debt securities: Amortized cost of $525 and $500, respectively)	522	501
Accounts receivable, net (Allowance for expected credit losses of $110 and $166, respectively)	1,555	529
Prepaid expenses, net (Allowance for expected credit losses of $15 and $22, respectively)	394	337
Other current assets	238	277
Total current assets	14,352	12,206
Property and equipment, net	762	756
Operating lease assets	445	529
Intangible assets, net	1,677	1,812
Goodwill	1,872	1,895
Long-term investments (Includes available-for-sale debt securities: Amortized cost of $200 and $225, respectively)	3,283	3,759
Other assets, net (Allowance for expected credit losses of $35 and $33, respectively)	950	917
Total assets	23,341	21,874
Current liabilities:
Accounts payable	1,466	735
Accrued expenses and other current liabilities	2,069	1,382
Deferred merchant bookings	1,086	323
Short-term debt	1,158	985
Total current liabilities	5,779	3,425
Deferred income taxes	906	1,127
Operating lease liabilities	295	366
Long-term U.S. transition tax liability	824	923
Other long-term liabilities	116	111
Long-term debt	9,876	11,029
Total liabilities	17,796	16,981
Commitments and contingencies (see Note 13)
Stockholders' equity:
Common stock, $0.008 par value, Authorized shares: 1,000,000,000 Issued shares: 63,580,079 and 63,406,451, respectively	0	0
Treasury stock, 22,516,608 and 22,446,897 shares, respectively	(24,286)	(24,128)
Additional paid-in capital	6,068	5,851
Retained earnings	23,835	23,288
Accumulated other comprehensive loss	(72)	(118)
Total stockholders' equity	5,545	4,893
Total liabilities and stockholders' equity	$ 23,341	$ 21,874

UNAUDITED CONSOLIDATED BALANC_2

UNAUDITED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Amortized cost of available-for-sale debt securities, current	$ 525	$ 500
Accounts receivable, allowance for expected credit losses	110	166
Prepaid expenses, allowance for expected credit losses, current	15	22
Amortized cost of available-for-sale debt securities, noncurrent	200	225
Other assets, allowance for expected credit losses, noncurrent	$ 35	$ 33
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)	63,580,079	63,406,451
Treasury stock, shares (in shares)	22,516,608	22,446,897

UNAUDITED CONSOLIDATED STATEMEN

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Total revenues	$ 4,676	$ 2,640	$ 7,977	$ 5,558
Operating expenses:
Marketing expenses	1,378	731	2,827	1,793
Sales and other expenses	302	129	620	637
Personnel, including stock-based compensation of $85, $80, $284 and $163, respectively	591	517	1,829	1,453
General and administrative	179	148	432	453
Information technology	109	71	289	219
Depreciation and amortization	102	115	323	344
Restructuring and other exit costs	0	41	9	75
Impairment of goodwill	0	573	0	1,062
Total operating expenses	2,661	2,325	6,329	6,036
Operating income (loss)	2,015	315	1,648	(478)
Interest expense	(80)	(98)	(259)	(258)
Other income (expense), net	(967)	618	(740)	1,058
Income before income taxes	968	835	649	322
Income tax expense	199	34	102	98
Net income	$ 769	$ 801	$ 547	$ 224
Net income applicable to common stockholders per basic common share (in dollars per share)	$ 18.73	$ 19.56	$ 13.33	$ 5.46
Weighted-average number of basic common shares outstanding (in shares)	41,068	40,935	41,032	40,983
Net income applicable to common stockholders per diluted common share (in dollars per share)	$ 18.60	$ 19.49	$ 13.22	$ 5.44
Weighted-average number of diluted common shares outstanding (in shares)	41,342	41,081	41,359	41,142
Agency revenues
Total revenues	$ 2,867	$ 1,723	$ 4,912	$ 3,504
Merchant revenues
Total revenues	1,622	837	2,656	1,741
Advertising and other revenues
Total revenues	$ 187	$ 80	$ 409	$ 313

UNAUDITED CONSOLIDATED STATEM_2

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Stock-based compensation expense	$ 85	$ 80	$ 284	$ 163

UNAUDITED CONSOLIDATED STATEM_3

UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income	$ 769	$ 801	$ 547	$ 224
Other comprehensive (loss) income, net of tax
Foreign currency translation adjustments, net of tax	(30)	42	(52)	(3)
Net unrealized gains (losses) on available-for-sale securities	1	(5)	98	(2)
Total other comprehensive (loss) income, net of tax	(29)	37	46	(5)
Comprehensive income	$ 740	$ 838	$ 593	$ 219

UNAUDITED CONSOLIDATED STATEM_4

UNAUDITED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Millions	Total	Cumulative Effect of Adoption of Accounting Standards Update	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Retained EarningsCumulative Effect of Adoption of Accounting Standards Update	Accumulated Other Comprehensive Loss
Balance (in shares) at Dec. 31, 2019			63,179	(21,762)
Balance at Dec. 31, 2019	$ 5,933	$ (3)	$ 0	$ (22,864)	$ 5,756	$ 23,232	$ (3)	$ (191)
Increase (Decrease) in Stockholders' Equity
Net income	224					224
Foreign currency translation adjustments, net of tax	(3)							(3)
Net unrealized gains on available-for-sale securities, net of tax	(2)							(2)
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)			220
Exercise of stock options and vesting of restricted stock units and performance share units	$ 6		$ 0		6
Repurchase of common stock (in shares)	(682)			(682)
Repurchase of common stock	$ (1,259)			$ (1,259)
Stock-based compensation and other stock-based payments	166				166
Balance (in shares) at Sep. 30, 2020			63,399	(22,444)
Balance at Sep. 30, 2020	4,913		$ 0	$ (24,123)	5,779	23,453		(196)
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)
Increase (Decrease) in Stockholders' Equity
Net income	801					801
Foreign currency translation adjustments, net of tax	42							42
Net unrealized gains on available-for-sale securities, net of tax	(5)							(5)
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)			8
Exercise of stock options and vesting of restricted stock units and performance share units	$ 0		$ 0		0
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 Sep. 30, 2020			63,399	(22,444)
Balance at Sep. 30, 2020	4,913		$ 0	$ (24,123)	5,779	23,453		(196)
Balance (in shares) at Dec. 31, 2020			63,406	(22,447)
Balance at Dec. 31, 2020	4,893		$ 0	$ (24,128)	5,851	23,288		(118)
Increase (Decrease) in Stockholders' Equity
Net income	547					547
Foreign currency translation adjustments, net of tax	(52)							(52)
Net unrealized gains on available-for-sale securities, net of tax	98							98
Conversion of debt	(86)				(86)
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)			174
Exercise of stock options and vesting of restricted stock units and performance share units	$ 4		$ 0		4
Repurchase of common stock (in shares)	(70)			(70)
Repurchase of common stock	$ (158)			$ (158)
Stock-based compensation and other stock-based payments	299				299
Balance (in shares) at Sep. 30, 2021			63,580	(22,517)
Balance at Sep. 30, 2021	5,545		$ 0	$ (24,286)	6,068	23,835		(72)
Balance (in shares) at Jun. 30, 2021			63,575	(22,515)
Balance at Jun. 30, 2021	4,799		$ 0	$ (24,283)	6,059	23,066		(43)
Increase (Decrease) in Stockholders' Equity
Net income	769					769
Foreign currency translation adjustments, net of tax	(30)							(30)
Net unrealized gains on available-for-sale securities, net of tax	1							1
Conversion of debt	(81)				(81)
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)			5
Exercise of stock options and vesting of restricted stock units and performance share units	$ 0		$ 0		0
Repurchase of common stock (in shares)	(2)			(2)
Repurchase of common stock	$ (3)			$ (3)
Stock-based compensation and other stock-based payments	90				90
Balance (in shares) at Sep. 30, 2021			63,580	(22,517)
Balance at Sep. 30, 2021	$ 5,545		$ 0	$ (24,286)	$ 6,068	$ 23,835		$ (72)

UNAUDITED CONSOLIDATED STATEM_5

UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020
OPERATING ACTIVITIES:
Net income		$ 547	$ 224
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		323	344
Provision for expected credit losses and chargebacks		88	307
Deferred income tax (benefit) expense		(343)	101
Net losses (gains) on equity securities	[1]	589	(1,261)
Stock-based compensation expense and other stock-based payments		290	179
Operating lease amortization		135	137
Amortization of debt discount and debt issuance costs		44	48
Unrealized foreign currency transaction (gains) losses on Euro-denominated debt		(108)	139
Impairment of goodwill		0	1,062
Impairment of investment	[1]	0	100
Loss on early extinguishment of debt	[2]	242	0
Other		17	3
Changes in assets and liabilities:
Accounts receivable		(1,172)	554
Prepaid expenses and other current assets		(35)	230
Deferred merchant bookings and other current liabilities		2,083	(1,593)
Other long-term assets and liabilities		(159)	88
Net cash provided by operating activities		2,541	662
INVESTING ACTIVITIES:
Purchase of investments		(15)	(72)
Proceeds from sale and maturity of investments		8	2,997
Additions to property and equipment		(203)	(222)
Other investing activities		(5)	0
Net cash (used in) provided by investing activities		(215)	2,703
FINANCING ACTIVITIES:
Proceeds from the issuance of long-term debt		2,015	4,108
Payments of debt issuance costs		(10)	(38)
Payments for redemption and conversion of debt		(3,068)	(1,244)
Payments for repurchase of common stock		(159)	(1,299)
Other financing activities		(12)	5
Net cash (used in) provided by financing activities		(1,234)	1,532
Effect of exchange rate changes on cash and cash equivalents and restricted cash and cash equivalents		(11)	(12)
Net increase in cash and cash equivalents and restricted cash and cash equivalents		1,081	4,885
Total cash and cash equivalents and restricted cash and cash equivalents, beginning of period		10,582	6,332
Total cash and cash equivalents and restricted cash and cash equivalents, end of period		11,663	11,217
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid during the period for income taxes (see Note 17)		420	152
Cash paid during the period for interest		$ 231	$ 158

[1]	See Note 5 for additional information related to the net (losses) gains on equity securities and impairment of investment.
[2]	See Note 9 for additional information related to the loss on early extinguishment of debt.

BASIS OF PRESENTATION

BASIS OF PRESENTATION	9 Months Ended
BASIS OF PRESENTATION	Sep. 30, 2021
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 ("U.S. 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 ("SEC") for interim reporting. As permitted under those rules, the Company condensed or omitted certain footnotes or other financial information that are normally required by U.S. 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, 2020. The Unaudited Consolidated Financial Statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances 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 "Other income (expense), net" 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 The ongoing outbreak of the novel strain of the coronavirus COVID-19 (the "COVID-19 pandemic"), as well as subsequent outbreaks driven by new variants of COVID-19, and the resulting economic conditions and government restrictions resulted in a material decrease in consumer spending and a significant decline in travel and restaurant activities and consumer demand for related services as compared to 2019 levels. See Note 2 to the Consolidated Financial Statements in the Company's Annual Report on Form 10-K for the year ended December 31, 2020 for further information. The Company’s financial results and prospects are almost entirely dependent on the sale of travel-related services. Governments around the world continue to implement a variety of measures to reduce the spread of COVID-19, including travel restrictions, bans and advisories, instructions to practice social distancing, curfews, quarantine advisories, including quarantine restrictions after travel in certain locations, shelter-in-place orders, required closures of non-essential businesses, vaccination mandates or requirements for businesses to confirm employees' vaccination status, and other restrictions. These government mandates have had a significant adverse effect on many of the customers on whom the Company’s business relies, including hotels and other accommodation providers, airlines and restaurants, as well as the Company's workforce, operations and consumers. Though some governments have started to relax COVID-19-related restrictions and vaccine distributions are well underway in some countries, there remains uncertainty around the impact of the new variants of COVID-19, when remaining restrictions will be lifted, if additional restrictions may be initiated or reimposed, if there will be changes to travel behavior patterns when government restrictions are fully lifted, and the timing of distribution and administration of COVID-19 vaccines globally. In 2020, given the severe downturn in the global travel industry and the financial difficulties faced by many of the Company's travel service provider and restaurant customers and marketing affiliates, the Company 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 incurred higher than normal cash outlays to refund consumers for prepaid reservations, including certain situations where the Company had already transferred the prepayment to the travel service provider (see Note 2). In 2021, based on its review of recent historical credit loss experience and stability in the economic conditions in certain markets, the Company revised its estimates of expected credit losses (see Note 7). Any significant increase in the Company's provision for expected credit losses and any significant increase in cash outlays to refund 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 recorded significant goodwill impairment charges in 2020 (see Note 8 ). In addition, the Company recorded a significant impairment ch arge in 2020 for one of the Company's long-term investments (see Notes 5 and 6). Even though no additional impairment indicators were identified as of September 30, 2021 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 1.7 billion Euros of debt issued in March 2021, payment of $2.0 billion in April 2021 to redeem certain Senior Notes issued in April 2020 and payment of $1.1 billion to satisfy the aggregate principal amount and the conversion premium in excess of the principal amount of the Senior Convertible Notes due September 2021. 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 the Company's credit ratings. While there have been some signs of a recovery in travel demand in many parts of the world including the United States and Europe as well as more recently in Asia, the Company continues to expect that its business will be adversely impacted by surges of COVID-19 case counts, including those driven by variants of COVID-19, as well as any government-imposed travel restrictions in reaction to COVID-19 outbreaks, which could remain a risk for an extended period of time. 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 COVID-19 pandemic, including as a result of any new variants of COVID-19 and any resurgences of the pandemic, the global distribution of the vaccines and their efficacy against existing and any future variants of COVID-19, and their impacts on the travel and restaurant industries and consumer spending more broadly. While vaccinations continue to advance throughout the world, many countries in Asia, Africa, South America, and other parts of the world have made slower progress. Additionally, the highly-transmissible Delta variant of COVID-19 has caused authorities in various countries to reimpose restrictions such as mask mandates, curfews and prohibitions on large gatherings. Even though there have been some improvements in the economic and operating conditions for the Company's business since the outset of the COVID-19 pandemic, 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, during the year ended December 31, 2020, the Company took actions to reduce the size of its workforce to optimize efficiency and reduce costs. See Note 14 for additional information. The Company also participated in certain governmental assistance programs and received certain grants and other assistance. In June 2021, the Company announced its intention to voluntarily return the government assistance received and has repai d $107 million as of September 30, 2021. See Note 15 for additional information. Reclassification Certain amounts from prior periods have been reclassified to conform to the current period presentation. Recent Accounting Pronouncements Adopted Simplifying the Accounting for Income Taxes The Financial Accounting Standards Board ("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. The Company adopted this update on January 1, 2021 and applied the applicable amendments on a prospective basis. The adoption did not have a material impact on the Company's Unaudited Consolidated Financial Statements. Other Recent Accounting Pronouncements Accounting for Acquired Revenue Contracts with Customers in a Business Combination In October 2021, the FASB issued a new accounting update that requires an acquirer to recognize and measure certain contract assets and contract liabilities in a business combination in accordance with Accounting Standards Codification ("ASC") 606, Revenue from Contracts with Customers , rather than at fair value on the acquisition date as required under current U.S. GAAP. The update is effective for the Company from January 1, 2023 and should be applied prospectively to business combinations occurring on or after that date. Early adoption is permitted. The Company is currently evaluating the impact to its Consolidated Financial Statements of adopting this update. 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 U.S. 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 update is effective for the Company from January 1, 2022. The update can be adopted on either a full or modified retrospective transition method. The Company is currently evaluating the impact to its Consolidated Financial Statements of adopting this update, including determining the transition method and establishing the related processes and controls. For the Company’s convertible debt instruments, interest expense for the periods subsequent to the adoption of the new accounting update will be reflected in the financial statements using interest rates that typically will be closer to the coupon interest rate of such instruments rather than a generally higher imputed interest expense that results from the separation of conversion features required by current U.S. GAAP. See Note 9 for additional information on the Company’s convertible debt instruments. The accounting update also requires changes in the diluted earnings per share calculation in certain areas, including the use of the if-converted method instead of the treasury stock method which was permitted in certain situations under current U.S. GAAP. See Note 4 for additional information on earnings per share.

REVENUE

REVENUE	9 Months Ended
REVENUE	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
REVENUE	REVENUE Disaggregation of Revenue Geographic Information The Company's international revenue 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 results of the Company's international businesses. The Company's geographic information is as follows (in millions): International United States The Netherlands Other Total Total revenues for the three months ended September 30, 2021 $ 444 $ 3,955 $ 277 $ 4,676 2020 $ 214 $ 2,231 $ 195 $ 2,640 Total revenues for the nine months ended September 30, 2021 $ 1,034 $ 6,367 $ 576 $ 7,977 2020 $ 604 $ 4,352 $ 602 $ 5,558 Revenue by Type of Service Approximately 89% and 87% of the Company's revenue for the three and nine months ended September 30, 2021, respectively, and 91% and 88% of the Company's revenue for the three and nine months ended September 30, 2020, respectively, relates to online accommodation reservation services. Revenue from all other sources of online travel reservation services and advertising and other revenues each individually represent less than 10% of the Company's total revenues for each period. Deferred Merchant Bookings and Deferred Revenue Cash payments received from travelers in advance of the Company completing its performance 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. At September 30, 2021 and December 31, 2020, deferred merchant bookings included deferred revenue for online travel reservation services of $163 million and $50 million, respectively. The amounts are subject to refunds for cancellations. The Company expects to complete its performance obligations generally within one year from the reservation date. During the nine months ended September 30, 2021, the Company recognized revenues of $34 million from the deferred revenue balance as of December 31, 2020. The increase in the deferred revenue balance for the nine months ended September 30, 2021 is principally driven by payments received from travelers, net of amounts estimated to be payable to travel service providers, for online travel reservations in the current period. Loyalty and Other Incentive Programs The Company provides loyalty programs, such as OpenTable's loyalty program, where participating consumers are awarded loyalty points on current transactions that can be redeemed in the future. At September 30, 2021 and December 31, 2020, liabilities for loyalty program incentives of $13 million and $21 million, respectively, were included in "Accrued expenses and other current liabilities" in the Consolidated Balance Sheets. 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 September 30, 2021 and December 31, 2020, liabilities of $61 million and $60 million, respectively, for other incentive programs, such as referral bonuses, rebates, credits and discounts, including for Booking.com's back-to-travel campaigns, were included in "Accrued expenses and other current liabilities" in the Consolidated Balance Sheets. Refunds to Travelers Due to the high level of cancellations of existing reservations as a result of the COVID-19 pandemic (see Note 1), in 2020, the Company incurred higher than normal cash outlays to refund travelers for prepaid reservations, including certain situations where the Company had already transferred the prepayment to the travel service provider. For the nine months ended September 30, 2020, the Company recorded a reduction in revenue of $42 million for refunds paid or estimated to be payable to travelers where the Company had agreed to provide free cancellation for certain non-refundable reservations without a corresponding estimated expected recovery from the travel service providers. For the three months ended September 30, 2020, the Company recorded an increase in revenue of $21 million due to recoveries from travel service providers and lower estimated payments to travelers.

STOCK-BASED EMPLOYEE COMPENSATI

STOCK-BASED EMPLOYEE COMPENSATION	9 Months Ended
STOCK-BASED EMPLOYEE COMPENSATION	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
STOCK-BASED EMPLOYEE COMPENSATION	STOCK-BASED EMPLOYEE COMPENSATION 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. For performance share units with market conditions, the effect of the market condition is also considered in the determination of fair value on the grant date using Monte Carlo simulations. 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 or performance goals, as applicable). 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 or expected achievement of performance goals, as applicable. Due to the impact of the COVID-19 pandemic (see Note 1), there was a significant decline, as of March 31, 2020, 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, for 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 nine months ended September 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 additional stock-based compensation expense of $11 million, which was recognized over the remaining requisite service period. During the three months ended March 31, 2021, the Company modified the performance-based awards granted in 2018 and 2019 to its executive officers, to fix the number of shares to be issued, subject to other vesting conditions. The modification, in the aggregate, resulted in additional stock-based compensation expense of $40 million , to be recognized over the remaining requisite service periods for the performance-based awards. Restricted stock units and performance share units granted by the Company during the three and nine months ended September 30, 2021 had an aggregate grant-date fair value of $22 million and $400 million, respectively. Restricted stock units and performance share units that vested during the three and nine months ended September 30, 2021 had an aggregate fair value at vesting of $8 million and $385 million, respectively. At September 30, 2021, there was $520 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 2.0 years. At September 30, 2021, there was $33 million of estimated total future stock-based compensation expense related to unvested stock options to be recognized over a weighted-average period of 1.4 years. Restricted Stock Units The Company makes broad-based grants of restricted stock units that generally vest during a period of one The following table summarizes the activity of restricted stock units for employees and non-employee directors during the nine months ended September 30, 2021: Restricted Stock Units Shares Weighted-average Grant-date Fair Value Unvested at December 31, 2020 305,959 $ 1,697 Granted 133,667 $ 2,270 Vested (114,486) $ 1,793 Forfeited (39,382) $ 1,882 Unvested at September 30, 2021 285,758 $ 1,901 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 (with the exception of certain shorter term performance share units granted in 2021 that vest at the end of one The following table summarizes the activity of performance share units for employees during the nine months ended September 30, 2021: Performance Share Units Shares Weighted-average Grant-date Fair Value Unvested at December 31, 2020 84,478 $ 1,930 Granted (1) 42,173 $ 2,287 Vested (55,426) $ 1,999 Performance shares adjustment (2) 44,346 $ 2,125 Forfeited (7,248) $ 1,792 Unvested at September 30, 2021 108,323 $ 2,123 (1) Excludes 12,251 performance share units awarded during the nine months ended September 30, 2021 for which the grant date under ASC 718, Compensation - Stock Compensation , has not yet been established. Among other conditions, for the grant date to be established, a mutual understanding is required to be reached between the Company and the employee of the key terms and conditions of the award, including the performance targets. The performance targets for each of the annual performance periods under the award are set at the beginning of the respective year. (2) Probable outcome for performance-based awards is updated based upon changes in actual and forecasted operating results or expected achievement of performance goals, as applicable, and the impact of modifications. The following table summarizes the estimated vesting, as of September 30, 2021, of performance share units granted in 2021, 2020 and 2019, net of forfeiture and vesting since the respective grant dates: Performance Share Units, by grant year 2021 (1) 2020 2019 Shares probable to be issued 63,523 11,752 33,048 Shares not subject to the achievement of minimum performance thresholds 28,198 — 33,048 Shares that could be issued if maximum performance thresholds are met 63,523 18,080 61,669 (1) Excludes performance share units awarded during the nine months ended September 30, 2021 for which the grant date under ASC 718 has not yet been established as disclosed above. Stock Options In 2020, the Company granted stock options to certain employees 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 following table summarizes the activity for stock options during the nine months ended September 30, 2021: Employee Stock Options Number of Shares Weighted-average Aggregate Weighted-average Remaining Contractual Term Balance, December 31, 2020 152,746 $ 1,401 $ 126 9.3 Exercised (3,592) $ 1,226 Forfeited (12,846) $ 1,411 Balance, September 30, 2021 136,308 $ 1,405 $ 132 8.5 Exercisable at September 30, 2021 1,293 $ 789 $ 2 1.9 The aggregate intrinsic value of employee stock options exercised during the nine months ended September 30, 2021 and 2020 was $4 million and $14 million, respectively.

NET INCOME PER SHARE

NET INCOME PER SHARE	9 Months Ended
NET INCOME PER SHARE	Sep. 30, 2021
Earnings Per Share [Abstract]
NET INCOME PER SHARE	NET INCOME PER SHARE The Company c omputes basic net income per share by dividing net income applicable to common stockholders by the weighted-average number of common shares outstanding during the period. Diluted net income per share is based upon the weighted-average number of common and common equivalent shares outstanding during the period. Common equivalent shares related to stock options, restricted stock units and performance share units are calculated using the treasury stock method. Performance share units are included in the weighted-average common equivalent shares based on the number of shares that would be issued if the end of the reporting period were the end of the performance period, if the result would be dilutive. The Company's convertible notes have net share settlement features requiring the Company upon conversion to settle the principal amount of the debt for cash and the conversion premium for cash or shares of the Company's common stock, at the Company's option. Under the treasury stock method, if the conversion prices for the convertible notes exceed the Company's average stock price for the period, the convertible notes generally have no impact on diluted net income per share. The convertible notes are included in the calculation of diluted net income per share if their inclusion is dilutive under the treasury stock method. A reconciliation of the weighted-average number of shares outstanding used in calculating diluted net income per share is as follows (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Weighted-average number of basic common shares outstanding 41,068 40,935 41,032 40,983 Weighted-average dilutive stock options, restricted stock units and performance share units 178 146 202 142 Assumed conversion of convertible senior notes 96 — 125 17 Weighted-average number of diluted common and common equivalent shares outstanding 41,342 41,081 41,359 41,142 For the nine months ended September 30, 2021, 15,434 potential common shares, and f or the three and nine months ended September 30, 2020, 163,507 and 165,923 potential common shares, respectively, related to stock options, restricted stock units and performance share units, as applicable, were excluded from the calculation of dilu t ed net income per share because their effect would have been anti-dilutive for the respective perio d.

INVESTMENTS

INVESTMENTS	9 Months Ended
INVESTMENTS	Sep. 30, 2021
Investments, Debt and Equity Securities [Abstract]
INVESTMENTS	INVESTMENTS The following table summarizes, by major security type, the Company's investments at September 30, 2021 (in millions): Cost Gross Gross Carrying Value Short-term investments: Debt securities: Trip.com Group convertible debt securities $ 525 $ — $ (3) $ 522 Long-term investments: Investments in private companies: Debt securities $ 200 $ 130 $ — $ 330 Equity securities 66 3 — 69 Other long-term investments: Equity securities 963 2,115 (194) 2,884 Total $ 1,229 $ 2,248 $ (194) $ 3,283 The following table summarizes, by major security type, the Company's investments at December 31, 2020 (in millions): Cost Gross Gross Unrealized Losses/Downward Adjustments Carrying Value Short-term investments: Debt securities: Trip.com Group convertible debt securities $ 500 $ 1 $ — $ 501 Long-term investments: Investments in private companies: Debt securities $ 200 $ — $ — $ 200 Equity securities 552 3 (100) 455 Other long-term investments: Debt securities: Trip.com Group convertible debt securities 25 — (1) 24 Equity securities 463 2,617 — 3,080 Total $ 1,240 $ 2,620 $ (101) $ 3,759 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 equity securities with readily determinable fair values and equity securities without readily determinable fair values. Equity securities with readily determinable fair values are reported at estimated fair value with changes in fair value recognized in "Other income (expense), net" 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 elected to measure these investments at cost less impairment, if any. Such investments are also required to be measured at fair value as of the date of certain observable transactions for the identical or a similar investment of the same issuer. During the nine months ended September 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 September 30, 2021, the Company had $525 million invested in convertible senior notes issued at par value by Trip.com Group including $25 million six-year convertible senior notes issued in September 2016 and $500 million ten-year convertible senior notes issued in December 2015. The $500 million convertible senior notes include a put option allowing the Company, at its option, to require a prepayment in cash from Trip.com Group at the end of the sixth year of the note. The $500 million convertible senior notes were classified as "Short-term investments" in the Consolidated Balance Sheets at September 30, 2021 and December 31, 2020 as the Company expects to exercise the put option and redeem the investment. The Company determined that the economic characteristics and risks of the put option related to the $500 million convertible senior notes 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 senior notes 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 "Short-term investments" or "Long-term investments," as applicable. The mark-to-market adjustments of the embedded derivative are included in "Other income (expense), net" in the Company's Unaudited Consolidated Statements of Operations. During the nine months ended September 30, 2020, the Company sold its entire investment in Trip.com Group American Depositary Shares ("ADSs"), with a cost basis of $655 million, for $525 million. "Other income (expense), net" in the Unaudited Consolidated Statement of Operations for the nine months ended September 30, 2020 includes a net realized loss of $201 million related to the sale of Trip.com Group ADSs. Investment in Meituan In 2017, the Company invested $450 million in preferred shares of Meituan, the leading e-commerce platform for local services in China. The investment has been converted to ordinary shares and classified as equity securities with readily determinable fair values since Meituan's initial public offering in 2018. The investment had a fair value of $2.6 billion and $3.1 billion at September 30, 2021 and December 31, 2020, respectively, which is included in "Long-term investments" in the Consolidated Balance Sheets. Net unrealized losses of $772 million and $509 million for the three and nine months ended September 30, 2021, respectively, and net unrealized gains of $727 million and $1.4 billion for the three and nine months ended September 30, 2020, respectively, related to this investment, are included in "Other income (expense), net" in the Unaudited Consolidated Statements of Operations. Investment in DiDi Global Inc. In 2018, the Company invested $500 million in preferred shares of DiDi Global Inc. ("DiDi"). The investment was classified as equity securities without readily determinable fair values and measured at cost less impairment, if any. The investment was also required to be measured at fair value as of the date of certain observable transactions for the identical or a similar investment issued by DiDi. In June 2021, DiDi announced the pricing of its initial public offering of ADSs, with four ADSs representing one Class A ordinary share, and its ADSs began publicly trading on the New York Stock Exchange. As a result of DiDi's initial public offering, the Company's investment was converted to Class A ordinary shares and classified as equity securities with readily determinable fair values. In connection with the initial public offering, the Company entered into a lock-up agreement with the underwriters. The lock-up agreement expires in December 2021 and restricts the sale, transfer or disposal by other means of the Company's investment in DiDi. The investment had a fair value of $306 million at September 30, 2021, which is included in "Long-term investments" in the Company's Consolidated Balance Sheet. The Company recorded unrealized losses of $249 million and $94 million in "Other income (expense), net" in the Unaudited Consolidated Statements of Operations for the three and nine months ended September 30, 2021, respectively. During the three months ended March 31, 2020, the Company recognized an impairment charge of $100 million to the investment due to the impact of the COVID-19 pandemic (see Note 1) that resulted in an adjusted carrying value of $400 million at each of March 31, 2020, December 31, 2020 and March 31, 2021 (see Note 6). Investments in Private Companies Equity Securities without Readily Determinable Fair Values The Company had $66 million and $552 million invested in equity securities of private companies at September 30, 2021 and December 31, 2020, respectively, including $51 million invested in Yanolja Co., Ltd. ("Yanolja"). These investments are measured at cost less impairment, if any. Such investments are also required to be measured at fair value as of the date of certain observable transactions for the identical or a similar investment of the same issuer. These investments are included in "Long-term investments" in the Company's Consolidated Balance Sheets. The investment balance at December 31, 2020 includes the Company's investment in DiDi, which was reclassified as equity securities with readily determinable fair values as disclosed above. In July 2021, Yanolja announced a new round of funding into the company. The new round of funding and certain other transactions in the equity securities of Yanolja were completed in October 2021. As a result of these observable transactions, the Company will measure its investment in Yanolja at fair value and expects that it will record an unrealized gain, before tax, of approximately $250 million during the three months ending December 31, 2021. Debt Securities The Company had $200 million invested in preferred shares of Grab Holdings Inc. ("Grab"), with an estimated fair value of $330 million and $200 million at September 30, 2021 and December 31, 2020, respectively (see Note 6). The investment in Grab is classified as a debt security 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. The investment is reported at its estimated fair value in "Long-term investments" in the Company's Consolidated Balance Sheets, with the aggregate unrealized gains and losses, net of tax, reflected in "Accumulated other comprehensive loss" in the Consolidated Balance Sheets. In April 2021, Grab announced its intention to pursue a public listing of its shares in the U.S. through a merger with Altimeter Growth Corp. ("Altimeter") (the "Grab Transaction"). The transaction is subject to certain closing conditions, including, the effectiveness of the relevant registration statement filed with the SEC and the approval of Altimeter and Grab shareholders. In connection with the proposed transaction, the Company has entered into a voting support and lock-up agreement with Grab. The voting support and lock-up agreement, among other things, restricts the sale or transfer of certain of the Company's shares in Grab for specified periods.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	9 Months Ended
FAIR VALUE MEASUREMENTS	Sep. 30, 2021
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS Financial assets and liabilities carried at fair value at September 30, 2021 and nonrecurring fair value measurements 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 $ 11,074 $ — $ — $ 11,074 Time deposits and certificates of deposit 41 — — 41 Short-term investments: Trip.com Group convertible debt securities — 522 — 522 Long-term investments: Investments in private companies: Debt securities — — 330 330 Other long-term investments: Equity securities 2,884 — — 2,884 Derivatives: Foreign currency exchange derivatives — 8 — 8 Total assets at fair value $ 13,999 $ 530 $ 330 $ 14,859 LIABILITIES: Foreign currency exchange derivatives $ — $ 11 $ — $ 11 Nonrecurring fair value measurements Investment in equity securities of a private company $ — $ 18 $ — $ 18 Financial assets and liabilities carried at fair value at December 31, 2020 and nonrecurring fair value measurements 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 $ 10,208 $ — $ — $ 10,208 Time deposits and certificates of deposit 32 — — 32 Short-term investments: Trip.com Group convertible debt securities — 501 — 501 Long-term investments: Investments in private companies: Debt securities — — 200 200 Other long-term investments: Trip.com Group convertible debt securities — 24 — 24 Equity securities 3,080 — — 3,080 Derivatives: Foreign currency exchange derivatives — 9 — 9 Total assets at fair value $ 13,320 $ 534 $ 200 $ 14,054 LIABILITIES: Foreign currency exchange derivatives $ — $ 7 $ — $ 7 Nonrecurring fair value measurements Investments in equity securities of private companies (1) $ — $ — $ 404 $ 404 Goodwill of the OpenTable and KAYAK reporting unit (2) — — 1,000 1,000 Total nonrecurring fair value measurements $ — $ — $ 1,404 $ 1,404 (1) At March 31, 2020, the investment in DiDi 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 the 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. At September 30, 2020, the goodwill was further written down to its estimated fair value of $1.0 billion, resulting in an additional impairment charge of $573 million (see Note 8). There are three levels of inputs to measure fair value. The definition of each input is described below: Level 1: Quoted prices in active markets that are accessible by the Company at the measurement date for identical assets and liabilities. Level 2: Inputs that are observable, either directly or indirectly. Such prices may be based upon quoted prices for identical or comparable securities in active markets or inputs not quoted on active markets, but corroborated by market data. Level 3: Unobservable inputs are used when little or no market data is available. Rollforward of Level 3 Fair Value Measurements The following table summarizes the fair value adjustments for debt securities measured using significant unobservable inputs (level 3) (in millions): For the Nine Months Ended September 30, 2021 2020 (1) Balance, beginning of year $ 200 $ 250 Unrealized gains included in accumulated other comprehensive loss (2) 130 — Balance, end of period $ 330 $ 250 (1) The Company recognized an unrealized loss of $20 million during the three months ended March 31, 2020 and an unrealized gain of $20 million during the three months ended June 30, 2020 related to the investment in Grab. (2) The unrealized gains are recorded in "Accumulated other comprehensive loss" in the Consolidated Balance Sheet. Investments See Note 5 for additional information related to the Company's investments. The valuation of investments in Trip.com Group convertible debt securities are considered "Level 2" valuations because the Company has access to quoted prices for identical or comparable securities, 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. As applicable, the Company also considers publicly disclosed information for certain merger transactions (not yet consummated), including those involving special purpose acquisition companies. 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. In certain situations, the current value method ("CVM") is utilized to allocate value to the various classes of equity based on their as-converted values. The OPM and CVM include assumptions around the investees' expected time to liquidity and volatility. The Company's investment in Grab, which is classified as a debt security for accounting purposes, had an estimated fair value of $330 million and $200 million at September 30, 2021 and December 31, 2020, respectively. At September 30, 2021, the Company measured this investment using Level 3 inputs and management's estimates that incorporate current market participant expectations of future cash flows alongside the Grab Transaction value and other relevant information. To estimate the fair value of Grab, the Company used a relative weighting of 70% market approach using the Grab Transaction value and 30% income approach. The market approach uses the Grab Transaction value and an estimated discount for the lack of marketability. The key unobservable inputs used include the volatility (65%) and an estimated time to liquidity of three months. 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 (12.0%-14.5%), terminal earnings before interest, taxes, depreciation and amortization ("EBITDA") multiple (12x-14x), volatility (60%-70%) and an estimated time to liquidity of five months. 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 value of Grab, inclusive of the consideration of the Grab Transaction value, reflects numerous assumptions that are subject to various risks and uncertainties, including the timing of when the transaction will be completed. The Grab Transaction is subject to certain closing conditions, including, the effectiveness of the relevant registration statement filed with the SEC and the approval of Altimeter and Grab shareholders. For the investment in the equity securities of DiDi, considering the impact of the COVID-19 pandemic (see Note 1), the Company performed an impairment analysis as of March 31, 2020 that resulted in an adjusted carrying value of $400 million at each of March 31, 2020, December 31, 2020 and March 31, 2021. As a result of DiDi's initial public offering, the Company reclassified its DiDi investment as equity securities with readily determinable fair values (see Note 5). Derivatives Derivatives not designated as hedges 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. Since the first quarter of 2020, the Company has not entered into such derivative instruments as the impact of the COVID-19 pandemic on the Company’s operating results is uncertain. The Company does not use derivatives for trading or speculative purposes. As of September 30, 2021 and December 31, 2020, the Company did not designate any foreign currency exchange derivatives as hedges for accounting purposes. The Company reports the fair values of its derivative assets and liabilities on a gross basis in the Consolidated Balance Sheets in "Other current assets" 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 "Other income (expense), net" 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 provided by operating activities" in the Unaudited Consolidated Statements of Cash Flows. The table below provides estimated fair values and notional amounts of foreign currency exchange derivatives outstanding at September 30, 2021 and December 31, 2020 (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. September 30, 2021 December 31, 2020 Estimated fair value of derivative assets $ 8 $ 9 Estimated fair value of derivative liabilities $ 11 $ 7 Notional amount: Foreign currency purchases $ 867 $ 898 Foreign currency sales $ 1,559 $ 839 The effect of foreign currency exchange derivatives recorded in "Other income (expense), net" in the Unaudited Consolidated Statements of Operations for the three and nine months ended September 30, 2021 and 2020 is as follows (in millions): Three Months Ended September 30, Nine Months Ended 2021 2020 2021 2020 Losses on foreign currency exchange derivatives $ 10 $ — $ 18 $ 31 Derivatives designated as cash flow hedges In March 2021, the Company entered into reverse treasury lock agreements with certain financial institutions, with an aggregate notional amount of $1.8 billion and expiration date of March 31, 2021, to hedge the risk of changes in the cash flows related to the planned redemption, in April 2021, of the Senior Notes due April 2025 (the "April 2025 Notes") and the Senior Notes due April 2027 (the "April 2027 Notes") attributable to changes in the underlying U.S. treasury notes' interest rates. The Company designated the reverse treasury lock agreements as cash flow hedges. As of March 31, 2021, th e Company recognized unrealized losses of $15 million in "Accumulated other comprehensive loss" in the Consolidated Balance Sheet. In April 2021, the Company settled the reverse treasury lock agreements for an aggregate amount of $15 million and also redeemed the April 2025 Notes and the April 2027 Notes. The cash flows related to the reverse treasury lock agreements are classified within "Net cash (used in) provided by financing activities" in the Unaudited Consolidated Statement of Cash Flows. During the three months ended June 30, 2021, the Company reclassified the losses on the cash flow hedges from "Accumulated other comprehensive loss" in the Consolidated Balance Sheet to "Other income (expense), net" in the Unaudited Consolidated Statement of Operations, concurrently with the recognition of the losses upon early extinguishment of the April 2025 Notes and the April 2027 Notes (see Note 9). Other Financial Assets and Liabilities At September 30, 2021 and December 31, 2020, 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 See Note 8 for nonrecurring fair value measurements related to the goodwill impairment test.

ACCOUNTS RECEIVABLE AND OTHER F

ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS	9 Months Ended
ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS	Sep. 30, 2021
Receivables [Abstract]
ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS	ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS Accounts receivable in the Consolidated Balance Sheets at September 30, 2021 and December 31, 2020 includes receivables from customers of $1.3 billion and $510 million, respectively, and receivables from marketing affiliates of $40 million and $32 million, respectively. The remaining balance principally 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 $68 million and $107 million included in "Prepaid expenses, net" and $35 million and $45 million included in "Other assets, net" in the Consolidated Balance Sheets at September 30, 2021 and December 31, 2020, respectively. The amounts mentioned above are stated on a gross basis, before deducting the allowance for expected credit losses. The Company has identified the relevant risk characteristics, of its customers and the related receivables and prepayments, which include the following: 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. In 2020, due to the impact of the COVID-19 pandemic (see Note 1), given the severe downturn in the global travel industry and the financial difficulties faced by many of the Company’s travel service provider and restaurant customers and marketing affiliates, the Company increased its provision for expected credit losses on receivables from and prepayments to its customers and marketing affiliates. Significant judgments and assumptions are required to estimate the allowance for expected credit losses 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 marketing affiliates and the Company’s ability to collect the receivable or recover the prepayment. In 2021, based on its review of recent historical credit loss experience and stability in the economic conditions in certain markets, the Company revised its estimates of expected credit losses. The following table summarizes the activity of the allowance for expected credit losses on receivables (in millions): Nine Months Ended 2021 2020 Balance, beginning of year $ 166 $ 49 Provision charged to earnings 44 206 Write-offs and adjustments (96) (59) Foreign currency translation adjustments (4) 12 Balance, end of period $ 110 $ 208 The allowance for expected credit losses on receivables 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. For the nine months ended September 30, 2021 and 2020, the Company recorded a reduction in revenue of $13 million and $32 million, respectively, for such refunds, which is included in "Provision charged to earnings" in the table above. In addition to the allowance for expected credit losses on receivables, the Company recorded an allowance for expected credit losses on prepayments to certain customers, which are included in "Prepaid expenses, net" and "Other assets, net" in the Consolidated Balance Sheets. The following table summarizes the activity of the allowance for expected credit losses on prepayments to customers (in millions): Nine Months Ended 2021 2020 Balance, beginning of year $ 55 $ 6 Provision charged to expense (2) 49 Write-offs and adjustments (3) (1) Balance, end of period $ 50 $ 54

GOODWILL, INTANGIBLE ASSETS AND

GOODWILL, INTANGIBLE ASSETS AND OTHER LONG-LIVED ASSETS	9 Months Ended
GOODWILL, INTANGIBLE ASSETS AND OTHER LONG-LIVED ASSETS	Sep. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL, INTANGIBLE ASSETS AND OTHER LONG-LIVED ASSETS	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 Company tests goodwill for impairment on an annual basis and between annual tests if 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 and the annual tests are performed as of September 30. As of September 30, 2021, the Company performed its annual goodwill impairment test and concluded that there was no impairment of goodwill. The balance of goodwill as of September 30, 2021 and December 31, 2020 is net of cumulative impairment charges of $2.0 billion. 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 and recognized a goodwill impairment charge of $489 million related to the OpenTable and KAYAK reporting unit for the three months ended March 31, 2020, which is not tax-deductible. As of September 30, 2020, the Company performed its annual goodwill impairment test and recognized a goodwill impairment charge of $573 million for the same reporting unit for the three months ended September 30, 2020, which is not tax-deductible. Intangible Assets and Other Long-lived Assets The Company's intangible assets at September 30, 2021 and December 31, 2020 consist of the following (in millions): September 30, 2021 December 31, 2020 Gross Accumulated Net Gross Accumulated Net Amortization Supply and distribution agreements $ 1,114 $ (582) $ 532 $ 1,136 $ (552) $ 584 3 - 20 years Technology 174 (149) 25 174 (144) 30 2 - 7 years Internet domain names 41 (36) 5 44 (37) 7 5 - 20 years Trade names 1,816 (701) 1,115 1,824 (633) 1,191 4 - 20 years Other intangible assets 2 (2) — 2 (2) — Up to 15 years Total intangible assets $ 3,147 $ (1,470) $ 1,677 $ 3,180 $ (1,368) $ 1,812 Intangible assets are amortized on a straight-line basis. Amortization expense was $40 million and $122 million for the three and nine months ended September 30, 2021, respectively, and $41 million and $126 million for the three and nine months ended September 30, 2020, 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. As of September 30, 2021 , no impairment indicators were identified for the Company's long-lived assets.

DEBT

DEBT	9 Months Ended
DEBT	Sep. 30, 2021
Debt Disclosure [Abstract]
DEBT	DEBT Revolving Credit Facility In August 2019, the Company entered into a $2.0 billion five-year unsecured revolving credit facility with a group of lenders. Borrowings under the revolving credit facility will bear interest, at the Company’s option, at a rate per annum equal to either (i) the London Inter-bank Offer Rate, or if such London Inter-bank Offer Rate is no longer available, the agreed alternate rate of interest ("LIBOR") (but no less than 0%) for the interest period in effect for such borrowing plus an applicable margin ranging from 0.875% to 1.50%; or (ii) for U.S. Dollar-denominated loans only, the sum of (x) the greatest of (a) JPMorgan Chase Bank, N.A.'s prime lending rate, (b) the U.S. federal funds rate plus 0.50% and (c) LIBOR (but no less than 0%) for an interest period of one month plus 1.00%, plus (y) an applicable margin ranging from 0% to 0.50%. Undrawn balances available under the revolving credit facility are subject to commitment fees at the applicable rate ranging from 0.07% to 0.20%. The revolving credit facility provides for the issuance of up to $80 million of letters of credit as well as borrowings of up to $100 million on same-day notice, referred to as swingline loans. Other than swingline loans, which are available only in U.S. Dollars, borrowings and letters of credit under the revolving credit facility may be made in U.S. Dollars, Euros, British Pounds Sterling and any other foreign currency agreed to by the lenders. The proceeds of loans made under the facility can be used for working capital and general corporate purposes, including acquisitions, share repurchases and debt repayments. At September 30, 2021 and December 31, 2020, there were no borrowings outstanding and $4 million of letters of credit issued under this revolving credit facility. 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 2020, the Company amended the revolving credit facility to (i) suspend the maximum leverage ratio covenant through and including the three months ending March 31, 2022, which was replaced with a $4.5 billion minimum liquidity covenant based on unrestricted cash, cash equivalents, short-term investments and unused capacity under this revolving credit facility and (ii) increase the permitted maximum leverage ratio from and including the three months ending June 30, 2022 through and including the three months ending March 31, 2023. The Company agreed not to declare or make any cash distribution and not to repurchase any of its shares (with certain exceptions including in connection with tax withholding related to shares issued to employees) unless (i) prior to the delivery of financial statements for the three months ending June 30, 2022, it has at least $6.0 billion of liquidity on a pro forma basis, based on unrestricted cash, cash equivalents, short-term investments and unused capacity under this revolving credit facility and (ii) after the delivery of financial statements for the three months ending June 30, 2022, it is in compliance on a pro forma basis with the maximum leverage ratio covenant then in effect. Such restriction ends upon delivery of financial statements required for the three months ending June 30, 2023, or the Company has the ability to terminate this restriction earlier if it demonstrates compliance with the original maximum leverage ratio covenant in the revolving credit facility. Beginning with the three months ending June 30, 2022, the minimum liquidity covenant will cease to apply and the maximum leverage ratio covenant, as increased, will again be in effect. Outstanding Debt Outstanding debt at September 30, 2021 consists of the following (in millions): September 30, 2021 Outstanding Principal Amount Unamortized Debt Carrying Value Current liabilities: 0.8% (€1 billion) Senior Notes due March 2022 $ 1,159 $ (1) $ 1,158 Long-term debt: 2.15% (€750 million) Senior Notes due November 2022 $ 869 $ (1) $ 868 2.75% Senior Notes due March 2023 500 (1) 499 2.375% (€1 billion) Senior Notes due September 2024 1,159 (5) 1,154 3.65% Senior Notes due March 2025 500 (2) 498 0.1% (€950 million) Senior Notes due March 2025 1,101 (5) 1,096 0.75% Convertible Senior Notes due May 2025 863 (106) 757 3.6% Senior Notes due June 2026 1,000 (4) 996 1.8% (€1 billion) Senior Notes due March 2027 1,159 (3) 1,156 3.55% Senior Notes due March 2028 500 (2) 498 0.5% (€750 million) Senior Notes due March 2028 869 (5) 864 4.625% Senior Notes due April 2030 1,500 (10) 1,490 Total long-term debt $ 10,020 $ (144) $ 9,876 Outstanding debt at December 31, 2020 consists of the following (in millions): December 31, 2020 Outstanding Unamortized Debt Carrying Value Current Liabilities: 0.9% Convertible Senior Notes due September 2021 $ 1,000 $ (15) $ 985 Long-term debt: 0.8% (€1 billion) Senior Notes due March 2022 $ 1,223 $ (1) $ 1,222 2.15% (€750 million) Senior Notes due November 2022 919 (4) 915 2.75% Senior Notes due March 2023 500 (1) 499 2.375% (€1 billion) Senior Notes due September 2024 1,223 (7) 1,216 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 (128) 735 3.6% Senior Notes due June 2026 1,000 (4) 996 1.8% (€1 billion) Senior Notes due March 2027 1,223 (2) 1,221 4.5% Senior Notes due April 2027 750 (5) 745 3.55% Senior Notes due March 2028 500 (2) 498 4.625% Senior Notes due April 2030 1,500 (11) 1,489 Total long-term debt $ 11,201 $ (172) $ 11,029 Fair Value of Debt At September 30, 2021 and December 31, 2020, the estimated fair value of the outstanding debt was approximately $12.3 billion and $14.0 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 conversion premium on the Convertible Senior Notes and the outstanding 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 $863 million aggregate principal amount of Convertible Senior Notes due May 2025 with an interest rate of 0.75% (the "May 2025 Notes"). The Company paid $19 million in debt issuance costs during the year ended December 31, 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. At September 30, 2021, the if-converted value of the May 2025 Notes exceeded the aggregate principal amount by $215 million. In August 2014, the Company issued $1.0 billion aggregate principal amount of Convertible Senior Notes due September 2021 with an interest rate of 0.9% (the "September 2021 Notes"). In September 2021, in connection with the maturity of the outstanding September 2021 Notes, the Company paid $1.0 billion to satisfy the aggregate principal amount due and paid an additional $86 million conversion premium in excess of the principal amount. In May 2013, the Company issued $1.0 billion aggregate principal amount of Convertible Senior Notes due June 15, 2020, with an interest rate of 0.35% (the "June 2020 Notes"). In June 2020, in connection with the maturity of the outstanding June 2020 Notes, the Company paid $1.0 billion to satisfy the aggregate principal amount due and paid an additional $245 million conversion premium 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 and 3.18% for the September 2021 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 and $83 million ($143 million before tax) related to the September 2021 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. Based on the closing price of the Company's common stock for the prescribed measurement periods for the three months ended September 30, 2021 and December 31, 2020, the contingent conversion thresholds on the May 2025 Notes were not exceeded and therefore the notes were not convertible . The following table summarizes the interest expenses and weighted-average effective interest rates related to the convertible senior notes (in millions, except for interest rates). The remaining period for amortization of debt discount and debt issuance costs is the period until the stated maturity date for the respective debt. For the Three Months Ended For the Nine Months Ended 2021 2020 2021 2020 Coupon interest expense $ 3 $ 4 $ 11 $ 11 Amortization of debt discount and debt issuance costs 12 13 36 42 Total interest expense $ 15 $ 17 $ 47 $ 53 Weighted-average effective interest rate 3.9 % 3.9 % 3.7 % 3.5 % Other Senior Notes In March 2021, the Company issued Senior Notes due March 2025 with an interest rate of 0.1% for an aggregate principal amount of 950 million Euros and Senior Notes due March 2028 with an interest rate of 0.5% for an aggregate principal amount of 750 million Euros. The proceeds from the issuance of these Senior Notes were used to redeem the April 2025 Notes and the April 2027 Notes. In March 2021, the Company delivered notices to the holders of the April 2025 Notes and the April 2027 Notes for the redemption, on April 3, 2021, of all the outstanding notes at the respective redemption prices determined as per the indenture governing the Notes, plus accrued and unpaid interest to, but not including the redemption date. In April 2021, the Company paid $1.1 billion and $868 million to redeem the April 2025 Notes and the April 2027 Notes, respectively. In addition, the Company paid the applicable accrued and unpaid interest. In the Unaudited Consolidated Statement of Operations for the nine months ending September 30, 2021, the Company recorded a loss, before tax, of $242 million on the early extinguishment of these Senior Notes, being the difference between the carrying value of the Notes and the amount paid for their redemption. Other senior notes, including the Senior Notes issued in March 2021, had a total carrying value of $10.3 billion at September 30, 2021 and December 31, 2020. Debt discount and debt issuance costs are 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 senior notes outstanding at September 30, 2021: Other Senior Notes Date of Issuance Effective Interest Rate (1) Timing of Interest Payments 0.8% Senior Notes due March 2022 March 2017 0.94 % Annually in March 2.15% Senior Notes due November 2022 November 2015 2.27 % Annually in November 2.75% Senior Notes due March 2023 August 2017 2.88 % Semi-annually in March and September 2.375% Senior Notes due September 2024 September 2014 2.54 % Annually in September 3.65% Senior Notes due March 2025 March 2015 3.76 % Semi-annually in March and September 0.1% Senior Notes due March 2025 March 2021 0.30 % Annually in March 3.6% Senior Notes due June 2026 May 2016 3.70 % Semi-annually in June and December 1.8% Senior Notes due March 2027 March 2015 1.86 % Annually in March 3.55% Senior Notes due March 2028 August 2017 3.63 % Semi-annually in March and September 0.5% Senior Notes due March 2028 March 2021 0.63 % Annually in March 4.625% Senior Notes due April 2030 April 2020 4.72 % Semi-annually in April and October (1) Represents the coupon interest rate adjusted for deferred debt issuance costs, premiums or discounts existing at the origination of the debt. The following table summarizes the interest expenses related to other senior notes (in millions): For the Three Months Ended For the Nine Months Ended 2021 2020 2021 2020 Coupon interest expense $ 60 $ 77 $ 198 $ 187 Amortization of debt discount and debt issuance costs 2 2 8 6 Total interest expense $ 62 $ 79 $ 206 $ 193 The Company designates certain portions of the aggregate principal value of the Euro-denominated debt as a hedge of the foreign currency exposure of the net investment in certain Euro functional currency subsidiaries. For the nine months ended September 30, 2021 and 2020, the carrying value of the portion of Euro-denominated debt, designated as a net investment hedge, ranged from $2.5 billion to $4.3 billion and from $1.8 billion to $3.2 billion, respectively. The foreign currency transaction gains or losses on the Euro-denominated debt that is designated as a hedging instrument for accounting purposes are recorded in "Accumulated other comprehensive loss" in the Consolidated Balance Sheets. The foreign currency transaction gains or losses on the Euro-denominated debt that is not designated as a hedging instrument are recognized i n " Other income (expense), net " in the Unaudited Consolidated Statements of Operations.

TREASURY STOCK

TREASURY STOCK	9 Months Ended
TREASURY STOCK	Sep. 30, 2021
Equity [Abstract]
TREASURY STOCK	TREASURY STOCK At September 30, 2021 and December 31, 2020, the Company had a total remaining authorization of $10.4 billion to repurchase its common stock under a program authorized by the Company's Board of Directors in 2019 to repurchase up to $15.0 billion of the Company's common stock. The Company has not repurchased any shares since March 2020 under this authorization and does not intend to initiate any repurchases under this authorization in 2021. Assuming the travel recovery continues and the Company is able to meet its minimum liquidity covenant under the revolving credit facility, the Company plans to start repurchases in early 2022 under this authorization, and expects to complete this authorization within three years after commencing repurchases. See Note 9 for a description of the impact of the 2020 credit facility amendment on the Company's ability to repurchase shares. 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 nine months ended September 30, 2021 and 2020 (in millions, except for shares, which are reflected in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Shares Amount Shares Amount Shares Amount Shares Amount Authorized stock repurchase programs — $ — — $ — — $ — 601 $ 1,122 General authorization for shares withheld on stock award vesting 2 3 2 4 70 158 81 137 Total 2 $ 3 2 $ 4 70 $ 158 682 $ 1,259 For the nine months ended September 30, 2021 and 2020, the Company remitted employee withholding taxes of $159 million and $137 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.

INCOME TAXES

INCOME TAXES	9 Months Ended
INCOME TAXES	Sep. 30, 2021
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 nine months ended September 30, 2021 were 20.5% and 15.8%, respectively, compared to 4.1% and 30.4% for the three and nine months ended September 30, 2020, respectively. The Company's 2021 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 (discussed below), partially offset by higher international tax rates, U.S. federal and state tax associated with the Company's international earnings, and certain non-deductible expenses. 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 charges related to OpenTable and KAYAK, the valuation allowance recorded against the deferred tax assets generated from the impairment of a long-term investment and an increase in unrecognized tax benefits, partially offset by the benefit of the Netherlands Innovation Box Tax. The Company’s effective tax rate for the three months ended September 30, 2021 was higher than the three months ended September 30, 2020, primarily due to a decrease in the benefit of the Netherlands Innovation Box Tax, partially offset by lower international tax rates, certain lower non-deductible expenses and a decrease in discrete U.S. tax expense related to unrealized gains on equity securities. In addition, the effective tax rate for the three months ended September 30, 2020 reflected the non-deductible goodwill impairment charge related to OpenTable and KAYAK. The Company’s effective tax rate for the nine months ended September 30, 2021 was lower than the nine months ended September 30, 2020, primarily due to lower discrete U.S. tax expense related to unrealized gains on equity securities, lower international tax rates and certain lower non-deductible expenses, partially offset by a decrease in the benefit of the Netherlands Innovation Box Tax. In addition, the effective tax rate for the nine months ended September 30, 2020 reflected the non-deductible goodwill impairment charge related to OpenTable and KAYAK. During the three and nine months ended September 30, 2021 and 2020, a majority of the Company's income was reported in the Netherlands, where Booking.com is based. According to Dutch corporate income tax law, income generated from qualifying innovative activities is taxed at a rate of 9% ("Innovation Box Tax") for periods beginning on or after January 1, 2021 rather than the Dutch statutory rate of 25%. Previously, the Innovation Box Tax rate had been 7%. A portion of Booking.com's earnings during the three and nine months ended September 30, 2021 and 2020 qualified for Innovation Box Tax treatment, which had a beneficial impact on the Company's effective tax rates for these periods. The aggregate amount of unrecognized tax benefits for all matters at September 30, 2021 and December 31, 2020 was $97 million and $84 million, respectively. The unrecognized tax benefits, if recognized, would impact the effective tax rate. As of September 30, 2021 and December 31, 2020, total gross interest and penalties accrued was $31 million. The majority of these unrecognized tax benefits are included in "Other long-term liabilities" and "Other assets, net" in the Consolidated Balance Sheets .

CHANGES IN ACCUMULATED OTHER CO

CHANGES IN ACCUMULATED OTHER COMPREHENSIVE LOSS BY COMPONENT	9 Months Ended
	Sep. 30, 2021
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
CHANGES IN ACCUMULATED OTHER COMPREHENSIVE LOSS BY COMPONENT	CHANGES IN ACCUMULATED OTHER COMPREHENSIVE LOSS BY COMPONENT The tables below present the changes in the balances of accumulated other comprehensive loss ("AOCI") by component for the three and nine months ended September 30, 2021 and 2020 (in millions): Foreign currency translation adjustments Unrealized losses on cash flow hedges (1) Net unrealized gains (losses) on available-for-sale securities Total AOCI, net of tax Foreign currency translation Net investment hedges (2) Total, net of tax Before tax Tax Total, net of tax Before tax Tax Total, net of tax Before tax Tax (3) Before tax Tax Three Months Ended September 30, 2021 Balance, June 30, 2021 $ (82) $ 50 $ (95) $ 16 $ (111) $ — $ — $ — $ 130 $ (62) $ 68 $ (43) Other comprehensive (loss) income ("OCI") before reclassifications (110) 10 93 (23) (30) — — — 1 — 1 (29) OCI for the period (110) 10 93 (23) (30) — — — 1 — 1 (29) Balance, September 30, 2021 $ (192) $ 60 $ (2) $ (7) $ (141) $ — $ — $ — $ 131 $ (62) $ 69 $ (72) Nine Months Ended September 30, 2021 Balance, December 31, 2020 $ 11 $ 47 $ (184) $ 37 $ (89) $ — $ — $ — $ 3 $ (32) $ (29) $ (118) OCI before reclassifications (203) 13 182 (44) (52) (15) 4 (11) 128 (30) 98 35 Amounts reclassified to (4) — — — — — 15 (4) 11 — — — 11 OCI for the period (203) 13 182 (44) (52) — — — 128 (30) 98 46 Balance, September 30, 2021 $ (192) $ 60 $ (2) $ (7) $ (141) $ — $ — $ — $ 131 $ (62) $ 69 $ (72) Foreign currency translation adjustments Unrealized losses on cash flow hedges (1) Net unrealized (losses) gains on available-for-sale securities Total AOCI, net of tax Foreign currency translation Net investment hedges (2) Total, net of tax Before tax Tax Total, net of tax Before tax Tax Total, net of tax Before tax Tax (3) Before tax Tax Three Months Ended September 30, 2020 Balance, June 30, 2020 $ (249) $ 58 $ 17 $ (10) $ (184) $ — $ — $ — $ (24) $ (25) $ (49) $ (233) OCI before reclassifications 99 (4) (69) 16 42 — — — (5) — (5) 37 OCI for the period 99 (4) (69) 16 42 — — — (5) — (5) 37 Balance, September 30, 2020 $ (150) $ 54 $ (52) $ 6 $ (142) $ — $ — $ — $ (29) $ (25) $ (54) $ (196) Nine Months Ended September 30, 2020 Balance, December 31, 2019 $ (186) $ 54 $ (2) $ (5) $ (139) $ — $ — $ — $ (7) $ (45) $ (52) $ (191) OCI before reclassifications 36 — (50) 11 (3) — — — (26) 6 (20) (23) Amounts reclassified to net income (4) — — — — — — — — 4 14 18 18 OCI for the period 36 — (50) 11 (3) — — — (22) 20 (2) (5) Balance, September 30, 2020 $ (150) $ 54 $ (52) $ 6 $ (142) $ — $ — $ — $ (29) $ (25) $ (54) $ (196) (1) Relates to the reverse treasury lock agreements entered in March 2021 that were designated as cash flow hedges and settled in April 2021 (see Note 6). (2) Net investment hedges balance at September 30, 2021 and earlier dates presented above, includes accumulated net losses from fair value adjustments of $35 million ($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 of the foreign currency exposure of the net investment in certain Euro functional currency subsidiaries (see Note 9). (3) 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"). (4) The reclassified losses before tax are included in "Other income (expense), net" and the related reclassified tax benefits 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 nine months ended September 30, 2020, the amounts reclassified to net income include 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. The tax expense is included in "Income tax expense" in the Unaudited Consolidated Statements of Operations.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
COMMITMENTS AND CONTINGENCIES	Sep. 30, 2021
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 and 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. These investigations can also result in fines and the Company had accrued liabilities of 14 million Euros ($17 million) and 18 million Euros ($23 million), for potential fines associated with its contractual parity arrangements, included in "Accrued expenses and other current liabilities" in the Consolidated Balance Sheets as of September 30, 2021 and December 31, 2020, respectively. 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, which resolved the CMA's investigation without a finding by the CMA of 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 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 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 multiple litigations in Israel claiming that it has violated Israeli consumer protection and competition laws. For example, 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 example of these lawsuits claims Israeli consumer protection laws prohibit the Company from facilitating non-refundable bookings to Israeli residents. Each of the plaintiffs in these various 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, the Company cannot reasonably estimate the amount of such potential damages because there are several unknown variables in each case at this early stage, including the likelihood of class certification, the size of any potential class and the likelihood of success of the merits of the claims. A German hotel association has initiated a class action lawsuit against Booking.com in Germany on behalf of a group of German hotels that alleges that the hotels overpaid commissions to Booking.com because of wide parity terms in the contracts between the hotels and Booking.com between 2006 and 2015. Booking.com is pursuing court proceedings in the Netherlands to declare that the Netherlands is the proper forum for this matter. Although the Company believes the claim to be without merit and intends to defend against the claim, if the hotel association were successful in its litigation and the Company were required to pay damages, the amount could be significant. The Company cannot reasonably estimate an amount of potential loss because there are several unknown variables at this early stage. 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 years 2013 through 2015 and currently are conducting an audit for the years 2016 through 2018. In December 2015, the French tax authorities issued Booking.com assessments for unpaid income and value added taxes ("VAT") related to tax years 2006 through 2012 for approximately 356 million Euros ($403 million), the majority of which represents penalties and interest. The assessments assert that Booking.com had a permanent establishment in France. In December 2019, the French tax authorities issued an additional assessment of 70 million Euros ($81 million), including interest and penalties, for the 2013 tax year asserting that Booking.com had taxable income attributable to a permanent establishment in France. The French tax authorities also have issued assessments totaling 39 million Euros ($45 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. As a result of a formal demand from the French tax authorities for payment of the amounts assessed against Booking.com 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 September 30, 2021 and December 31, 2020, 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. In December 2019 and October 2020, the Company initiated court proceedings with respect to certain of the assessments. Although 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, during the three months ended September 30, 2020, the Company contacted the French tax authorities regarding the potential to achieve resolution of the matter through a settlement. After assessing several potential outcomes and potential settlement amounts and terms, an unrecognized tax benefit in the amount of 50 million Euros ($59 million) was recorded during the year ended December 31, 2020, of which the majority was included as a partial reduction to the tax payment recorded in "Other assets, net" in the Consolidated Balance Sheets at September 30, 2021 and December 31, 2020. In December 2020, the French Administrative Court (Conseil d’Etat) delivered a decision in the "ValueClick" case that could have an impact on the outcome in the Company's case. After considering the potential adverse impact of the new decision on the potential outcomes for the Booking.com assessments, the Company currently estimates that the reasonably possible loss related to VAT is approximately 20 million Euros ($23 million). Additional assessments could result when the French tax authorities complete the outstanding audits. In December 2018 and December 2019, the Italian tax authorities issued assessments on Booking.com's Italian subsidiary for approximately 48 million Euros ($55 million) for the 2013 tax year and 58 million Euros ($67 million) for the 2014 tax year asserting that its transfer pricing policies were inadequate. The Company believes Booking.com has been and continues to be in compliance with Italian tax law. In September 2020, the Italian tax authorities approved the opening of a Mutual Agreement Procedure ("MAP") between Italy and the Netherlands for the 2013 tax year and Booking.com has submitted a request that the 2014 tax year be added to the MAP. Based on the possibility of the 2013 and 2014 Italian assessments being settled through the MAP process, and, after considering potential resolution amounts, a net unrecognized tax benefit amount of 4 million Euros ($5 million) was recorded during the three months ended September 30, 2020. In March 2021, the Italian authorities issued assessments on Booking.com’s Italian subsidiary for approximately 31 million Euros ($37 million) for the 2015 tax year, again asserting that its transfer pricing policies were inadequate. Based on the Company’s expectation that the Italian assessments for 2013, 2014, 2015 and any transfer pricing assessments received for subsequent open years will be settled through the MAP process, and after considering potential resolution amounts, an additional net unrecognized tax benefit of 13 million Euros ($16 million) was recorded during the three months ended March 31, 2021. In August 2021, the Italian tax authorities issued a transfer pricing assessment on Booking.com’s Italian subsidiary for approximately 114 million Euros ($132 million) for the periods 2016-2018. The Company intends to submit a request that the 2016-2018 assessment be added to the MAP. Because the unrecognized tax benefit recorded during the three months ended March 31, 2021 already reflected consideration of potential resolution amounts for Italian transfer pricing assessments for all open tax years, including 2016-2018, no additional unrecognized tax benefit has been recorded during the three months ended September 30, 2021. In December 2019, the Company paid 10 million Euros ($11 million) as a partial prepayment of the 2013 assessment to avoid any collection enforcement from the Italian tax authorities pending the appeal phase of the case. The payment, which is included in "Other assets, net" in the Consolidated Balance Sheets at September 30, 2021 and December 31, 2020, does not constitute an admission that the Company owes the taxes and will be refunded (with interest) to the Company to the extent that the Company prevails. A total of 5 million Euros ($6 million) of the net unrecognized tax benefits recorded during the nine months ended September 30, 2021 and the year ended December 31, 2020 has been included as a partial reduction to the tax payment recorded in "Other assets, net" in the Consolidated Balance Sheets at September 30, 2021 and December 31, 2020. Similarly, the Company expects to be required to make prepayment deposits or provide bank guarantees of approximately 60 million Euros ($70 million), which is equal to one-third of the interest and taxes for the 2014, 2015 and 2016-2018 assessments to avoid any collection enforcement from the Italian tax authorities pending the MAP proceedings. In June 2021, the investigative arm of the Italian tax authorities issued a Tax Audit Report for the 2013 through 2019 Italian VAT audit. While the Tax Audit Report does not constitute a formal tax assessment, it recommends that an assessment of 154 million Euros ($178 million), plus interest and penalties, should be made on Booking.com BV for VAT related to commissions charged to certain Italian accommodation providers. The Company believes that Booking.com has been, and continues to be, in compliance with Italian and EU VAT laws and the Company has not recorded any liability in connection with the Tax Audit Report. It is unclear what further actions, if any, the Italian authorities will take with respect to the VAT audit for the periods 2013 through 2019. Such actions could include closing the investigation, assessing Booking.com additional taxes and/or imposing interest, fines, penalties or criminal proceedings. In 2018 and 2019, Turkish tax authorities asserted that Booking.com has a permanent establishment in Turkey and have issued tax assessments for the years 2012 through 2018 for approximately 801 million Turkish Lira ($90 million), which includes interest and penalties through September 30, 2021. 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. In September 2021, the Swiss tax authorities issued an assessment for the amount of approximately 50 million Swiss Francs ($54 million), for VAT related to commissions charged to Swiss accommodation providers for the years 2015 through 2020. The Company believes that Booking.com has been, and continues to be, in compliance with Swiss VAT laws and the Company is contesting the assessment. The Company has not recorded any liability in connection with the assessment. In October 2021, Booking.com BV received a notice of proposed assessment of approximately $20 million from the state of Hawaii for the tax years 2010 to 2020. The notice of proposed assessment asserts that Booking.com BV is subject to Hawaii's general excise tax. The Company believes that Booking.com has been, and continues to be, in compliance with Hawaii state tax law, and the Company is contesting this assessment. The Company has not recorded a liability in connection with this assessment. As a result of an internal review of tax policies and positions at one of the Company's smaller subsidiaries in 2018, the Company identified two issues related to the application of certain non-income-based tax laws to that subsidiary's business. At September 30, 2021 and December 31, 2020, the Company had accrued $54 million and $59 million, respectively, 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 $20 million. 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, 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.). In May 2021, Clark County, Nevada filed a suit against the Company and other third-party OTCs alleging an underpayment of hotel occupancy taxes. The Company believes that the tax laws at issue do not apply to the services it provides, and, therefore, that it does not owe the taxes alleged to be owed. Although the Company intends to defend itself against the lawsuit, if there was an adverse outcome in this litigation, it could result in liabilities for past and/or future bookings, and it is unknown whether the liability would include interest, penalties, punitive damages and/or attorney’s fees and costs. At this early stage the Company cannot reasonably estimate the amount of any potential loss or range of loss. 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, in each case by ruling that Booking.com does not meet the definition of a travel intermediary for purposes of the mandatory pension scheme. BPF then appealed to the Netherlands Supreme Court. In April 2021, the Supreme Court overturned the previous decision of the Court of Appeal and held that Booking.com meets the definition of a travel intermediary for the purposes of the mandatory pension scheme. The Supreme Court ruled only on the qualification of Booking.com as a travel intermediary for the purposes of the mandatory pension scheme, and did not rule on the various other defenses brought forward by the Company against BPF's claims. The Supreme Court referred the matter to another Court of Appeal that will have to assess the other defenses brought forward by the Company if BPF were to proceed with the litigation. The Company intends to pursue a number of defenses in any subsequent proceedings and may ultimately prevail in whole or in part. While the Company continues to believe that Booking.com is in compliance with its pension obligations and that the Court of Appeal could ultimately rule in favor of Booking.com, given the Supreme Court’s decision, the Company believes it is probable that it has incurred a loss related to this matter. The Company is not able to reasonably estimate a loss or a range of loss because there are significant factual and legal questions yet to be determined in any subsequent proceedings. As a result, as of September 30, 2021, the Company has not recorded a liability in connection with a potential adverse ultimate outcome to this litigation. However, if Booking.com were to ultimately lose and all of BPF’s claims were to be accepted (including with retroactive effect to 1999), the Company estimates that as of September 30, 2021, the maximum loss, not including any potential interest or penalties, would be approximately 278 million Euros ($322 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 September 30, 2021. From time to time the Company notifies data protection authorities in various jurisdictions in accordance with its obligations under applicable data protection regulations, including its notification obligations of certain incidental and accidental personal data security incidents to the Dutch data protection authority in accordance with the E.U. General Data Protection Regulation. Although the Company believes it has fulfilled its data protection regulatory obligations including those to the Dutch data protection authority, should any data protection authority decide these incidents were the result of inadequate technical and organizational security measures, such authority could decide to impose a fine. While the Company believes that any fine imposed on it relating to such obligations would be immaterial, the Company estimates that if a fine were imposed by the Dutch data protection authority, it could range from a de minimis amount to 20 million Euros ($23 million) per incident, depending on the Dutch data protection authority’s evaluation of the facts and circumstances associated with the incident after investigation. The Company's alternative accommodation reservation business is subject to various laws, rules and regulations. These laws, rules and regulations are complex, vary by jurisdiction and their interpretation is rapidly evolving. From time to time, the Company is subject to inquiries related to compliance with alternative accommodation laws, rules and regulations that it may or may not be able to respond to in a timely manner or in full satisfaction of such requests. The outcome of such inquiries has resulted in fines and could require modifications to the Company’s business plans or operations, which could result in increased legal and compliance costs. As governments adopt new laws, rules and regulations related to alternative accommodations, the Company is unable to predict what, if any, effect any such future laws, rules and regulations will have on its business. 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, is currently, 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 for 270 million Euros ($313 million). 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 September 30, 2021, the Company had a remaining obligation of 22 million Euros ($25 million) related to the turnkey agreement, which will be paid through 2022, when the Company anticipates construction will be complete. In addition to the turnkey agreement, the Company has a remaining obligation at September 30, 2021 to pay 69 million Euros ($79 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. At September 30, 2021, the Company had 27 million Euros ($31 million) of outstanding commitments to vendors to fit out and furnish the office space. Other Contractual Obligations In 2018, the Company entered into an agreement to sign a future lease for office space in Manchester, United Kingdom for the future headquarters of Rentalcars.com, whereby the Company's obligation to execute the lease was conditional upon the lessor completing certain activities. The lease commenced in October 2021, with modifications to certain terms and conditions of the 2018 agreement, for a term of approximately 13 years with a lease payment obligation of approximately 52 million British Pounds Sterling ($71 million), excluding lease incentives. In addition to its obligations under the lease, the Company will also make capital expenditures to fit out and furnish the office space.

RESTRUCTURING AND OTHER EXIT CO

RESTRUCTURING AND OTHER EXIT COSTS	9 Months Ended
RESTRUCTURING AND OTHER EXIT COSTS	Sep. 30, 2021
Restructuring and Related Activities [Abstract]
RESTRUCTURING AND OTHER EXIT COSTS	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), during the year ended December 31, 2020, the Company took actions at all its brands to reduce the size of its workforce across more than 60 countries to optimize efficiency and reduce costs. As part of these actions, the Company engaged in consultations, with its employees, works councils, employee representatives and other relevant organizations related to the reductions in force in certain countries (including the Netherlands and the United Kingdom), which have substantially concluded as of December 31, 2020. These consultations resulted in the Company executing either voluntary leaver schemes or involuntary reductions in force, or, in some countries, a combination of the two. The Company completed the vast majority of announcements to affected employees by December 2020. During the nine months ended September 30, 2021, the Company approved and communicated the final portion of workforce reductions in the Netherlands, France and several other countries. During the nine months ended September 30, 2021, the Company recorded expenses of $9 million for the restructuring actions, which are included in " Restructuring and other exit costs" in the Unaudited Consolidated Statement of Operations. These expenses are primarily cash-based and consist of employee severance and other termination benefits, and other costs. During the nine months ended September 30, 2021, the Company made payments of $37 million. Noncash restructuring expenses and other adjustments to the restructuring liability during the nine months ended September 30, 2021 were $5 million. At September 30, 2021 and December 31, 2020, restructuring liabilities of $4 million and $37 million, respectively, are included in " Accrued expenses and other current liabilities " in the Consolidated Balance Sheets. As of September 30, 2021 , the Company estimates that it will record additional restructuring and other exit costs of approximately $7 million, primarily related to leases, in the remainder of 2021, with $4 million recorded thereafter. This estimate may change as the Company finalizes the execution of its cost reduction plans. The Company’s evaluation of various alternative courses of action related to certain other leases and contract terminations and modifications is still in progress and the Company may incur additional costs resulting from such actions.

GOVERNMENT GRANTS AND OTHER ASS

GOVERNMENT GRANTS AND OTHER ASSISTANCE	9 Months Ended
GOVERNMENT GRANTS AND OTHER ASSISTANCE	Sep. 30, 2021
Unusual or Infrequent Items, or Both [Abstract]
GOVERNMENT GRANTS AND OTHER ASSISTANCE	GOVERNMENT GRANTS AND OTHER ASSISTANCE Certain governments passed legislation to help businesses during the COVID-19 pandemic through loans, wage subsidies, tax relief or other financial aid. During the year ended December 31, 2020 and the three months ended March 31, 2021, the Company part icipated in several of these programs and recognized, in the aggregate, government grants and other assistance benefits of $131 million, principally recorded as a reduction of "Personnel" expense in the Consolidated Statement of Operations for the respective periods. As of March 31, 2021, the Company had a receivable of $28 million for payments expected to be received for the programs where it had met the qualifying requirements. In June 2021, the Company announced its intention to voluntarily return assistance received through various government aid programs and, for the nine months ended September 30, 2021, the Company recorded expenses of $137 million in the Unaudited Consolidated Statement of Operations, principally in " Personnel" expense, to reflect the return of such assistance. The Company repaid $107 million of assistance during the nine months ended September 30, 2021. The previously recorded receivable for payments expected to be received was also written off in June 2021. During the three and nine months ended September 30, 2020, the Company recognized government grants and other assistance benefits of $22 million and $122 million, respectively .

OTHER INCOME (EXPENSE), NET

OTHER INCOME (EXPENSE), NET	9 Months Ended
OTHER INCOME (EXPENSE), NET	Sep. 30, 2021
Other Income and Expenses [Abstract]
OTHER INCOME (EXPENSE), NET	OTHER INCOME (EXPENSE), NET The components of other income (expense), net included the following (in millions): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Interest and dividend income $ 4 $ 5 $ 12 $ 49 Net (losses) gains on equity securities (1) (1,016) 733 (589) 1,261 Impairment of investment (1) — — — (100) Foreign currency transaction gains (losses) 45 (121) 92 (148) Loss on early extinguishment of debt (2) — — (242) — Other (3) — 1 (13) (4) Other income (expense), net $ (967) $ 618 $ (740) $ 1,058 (1) See Note 5 for additional information related to the net (losses) gains on equity securities and impairment of investment. (2) See Note 9 for additional information related to the loss on early extinguishment of debt. (3) The amount for the nine months ended September 30, 2021 includes losses on reverse treasury lock agreements which were designated as cash flow hedges (see Note 6).

OTHER

OTHER	9 Months Ended
OTHER	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
OTHER	OTHER Unaudited Consolidated Statements of Cash Flows: Additional Information Restricted cash and cash equivalents at September 30, 2021 and December 31, 2020 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): September 30, December 31, (Unaudited) As included in the Consolidated Balance Sheets: Cash and cash equivalents $ 11,643 $ 10,562 Restricted cash and cash equivalents included in "Other current assets" 20 20 Total cash and cash equivalents and restricted cash and cash equivalents as shown in the Unaudited Consolidated Statements of Cash Flows $ 11,663 $ 10,582 During the nine months ended September 30, 2021, the Company prepaid Netherlands income taxes of 149 million Euros ($175 million).

BASIS OF PRESENTATION (Policies

BASIS OF PRESENTATION (Policies)	9 Months Ended
BASIS OF PRESENTATION (Policies)	Sep. 30, 2021
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 ("U.S. 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 ("SEC") for interim reporting. As permitted under those rules, the Company condensed or omitted certain footnotes or other financial information that are normally required by U.S. 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, 2020. The Unaudited Consolidated Financial Statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances 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 "Other income (expense), net" 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.
Reclassification	Reclassification Certain amounts from prior periods have been reclassified to conform to the current period presentation.
Recent Accounting Pronouncements Adopted and Other Recent Accounting Pronouncements	Recent Accounting Pronouncements Adopted Simplifying the Accounting for Income Taxes The Financial Accounting Standards Board ("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. The Company adopted this update on January 1, 2021 and applied the applicable amendments on a prospective basis. The adoption did not have a material impact on the Company's Unaudited Consolidated Financial Statements. Other Recent Accounting Pronouncements Accounting for Acquired Revenue Contracts with Customers in a Business Combination In October 2021, the FASB issued a new accounting update that requires an acquirer to recognize and measure certain contract assets and contract liabilities in a business combination in accordance with Accounting Standards Codification ("ASC") 606, Revenue from Contracts with Customers , rather than at fair value on the acquisition date as required under current U.S. GAAP. The update is effective for the Company from January 1, 2023 and should be applied prospectively to business combinations occurring on or after that date. Early adoption is permitted. The Company is currently evaluating the impact to its Consolidated Financial Statements of adopting this update. 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 U.S. 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 update is effective for the Company from January 1, 2022. The update can be adopted on either a full or modified retrospective transition method. The Company is currently evaluating the impact to its Consolidated Financial Statements of adopting this update, including determining the transition method and establishing the related processes and controls. For the Company’s convertible debt instruments, interest expense for the periods subsequent to the adoption of the new accounting update will be reflected in the financial statements using interest rates that typically will be closer to the coupon interest rate of such instruments rather than a generally higher imputed interest expense that results from the separation of conversion features required by current U.S. GAAP. See Note 9 for additional information on the Company’s convertible debt instruments. The accounting update also requires changes in the diluted earnings per share calculation in certain areas, including the use of the if-converted method instead of the treasury stock method which was permitted in certain situations under current U.S. GAAP. See Note 4 for additional information on earnings per share.
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. For performance share units with market conditions, the effect of the market condition is also considered in the determination of fair value on the grant date using Monte Carlo simulations. 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 or performance goals, as applicable). The Company periodically adjusts the cumulative stock-based compensation expense
Earnings Per Share	The Company c omputes basic net income per share by dividing net income applicable to common stockholders by the weighted-average number of common shares outstanding during the period. Diluted net income per share is based upon the weighted-average number of common and common equivalent shares outstanding during the period. Common equivalent shares related to stock options, restricted stock units and performance share units are calculated using the treasury stock method. Performance share units are included in the weighted-average common equivalent shares based on the number of shares that would be issued if the end of the reporting period were the end of the performance period, if the result would be dilutive. The Company's convertible notes have net share settlement features requiring the Company upon conversion to settle the principal amount of the debt for cash and the conversion premium for cash or shares of the Company's common stock, at the Company's option. Under the treasury stock method, if the conversion prices for the convertible notes exceed the Company's average stock price for the period, the convertible notes generally have no impact on diluted net income per share. The convertible notes are included in the calculation of diluted net income per share if their inclusion is dilutive under the treasury stock method.
Investment	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 equity securities with readily determinable fair values and equity securities without readily determinable fair values. Equity securities with readily determinable fair values are reported at estimated fair value with changes in fair value recognized in "Other income (expense), net" 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 elected to measure these investments at cost less impairment, if any. Such investments are also required to be measured at fair value as of the date of certain observable transactions for the identical or a similar investment of the same issuer.
Fair Value Measurement	Investments See Note 5 for additional information related to the Company's investments. The valuation of investments in Trip.com Group convertible debt securities are considered "Level 2" valuations because the Company has access to quoted prices for identical or comparable securities, 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. As applicable, the Company also considers publicly disclosed information for certain merger transactions (not yet consummated), including those involving special purpose acquisition companies. 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. In certain situations, the current value method ("CVM") is utilized to allocate value to the various classes of equity based on their as-converted values. The OPM and CVM include assumptions around the investees' expected time to liquidity and volatility.
Accounts Receivable and Allowance for Credit Losses	The Company has identified the relevant risk characteristics, of its customers and the related receivables and prepayments, which include the following: 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.
Goodwill	The Company tests goodwill for impairment on an annual basis and between annual tests if 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 and the annual tests are performed as of September 30. As of September 30, 2021, the Company performed its annual goodwill impairment test and concluded that there was no impairment of goodwill. The balance of goodwill as of September 30, 2021 and December 31, 2020 is net of cumulative impairment charges of $2.0 billion.
Long-Lived Assets, Including Intangible Assets and Operating Lease Assets	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 Tax	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)	9 Months Ended
REVENUE (Tables)	Sep. 30, 2021
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 September 30, 2021 $ 444 $ 3,955 $ 277 $ 4,676 2020 $ 214 $ 2,231 $ 195 $ 2,640 Total revenues for the nine months ended September 30, 2021 $ 1,034 $ 6,367 $ 576 $ 7,977 2020 $ 604 $ 4,352 $ 602 $ 5,558

STOCK-BASED EMPLOYEE COMPENSA_2

STOCK-BASED EMPLOYEE COMPENSATION (Tables)	9 Months Ended
STOCK-BASED EMPLOYEE COMPENSATION (Tables)	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Activity of Restricted Stock Units	The following table summarizes the activity of restricted stock units for employees and non-employee directors during the nine months ended September 30, 2021: Restricted Stock Units Shares Weighted-average Grant-date Fair Value Unvested at December 31, 2020 305,959 $ 1,697 Granted 133,667 $ 2,270 Vested (114,486) $ 1,793 Forfeited (39,382) $ 1,882 Unvested at September 30, 2021 285,758 $ 1,901
Activity of Performance Share Units	The following table summarizes the activity of performance share units for employees during the nine months ended September 30, 2021: Performance Share Units Shares Weighted-average Grant-date Fair Value Unvested at December 31, 2020 84,478 $ 1,930 Granted (1) 42,173 $ 2,287 Vested (55,426) $ 1,999 Performance shares adjustment (2) 44,346 $ 2,125 Forfeited (7,248) $ 1,792 Unvested at September 30, 2021 108,323 $ 2,123 (1) Excludes 12,251 performance share units awarded during the nine months ended September 30, 2021 for which the grant date under ASC 718, Compensation - Stock Compensation , has not yet been established. Among other conditions, for the grant date to be established, a mutual understanding is required to be reached between the Company and the employee of the key terms and conditions of the award, including the performance targets. The performance targets for each of the annual performance periods under the award are set at the beginning of the respective year. (2) Probable outcome for performance-based awards is updated based upon changes in actual and forecasted operating results or expected achievement of performance goals, as applicable, and the impact of modifications.
Estimated Vesting of Performance Share Units Granted	The following table summarizes the estimated vesting, as of September 30, 2021, of performance share units granted in 2021, 2020 and 2019, net of forfeiture and vesting since the respective grant dates: Performance Share Units, by grant year 2021 (1) 2020 2019 Shares probable to be issued 63,523 11,752 33,048 Shares not subject to the achievement of minimum performance thresholds 28,198 — 33,048 Shares that could be issued if maximum performance thresholds are met 63,523 18,080 61,669 (1) Excludes performance share units awarded during the nine months ended September 30, 2021 for which the grant date under ASC 718 has not yet been established as disclosed above.
Activity for Stock Options	The following table summarizes the activity for stock options during the nine months ended September 30, 2021: Employee Stock Options Number of Shares Weighted-average Aggregate Weighted-average Remaining Contractual Term Balance, December 31, 2020 152,746 $ 1,401 $ 126 9.3 Exercised (3,592) $ 1,226 Forfeited (12,846) $ 1,411 Balance, September 30, 2021 136,308 $ 1,405 $ 132 8.5 Exercisable at September 30, 2021 1,293 $ 789 $ 2 1.9

NET INCOME PER SHARE (Tables)

NET INCOME PER SHARE (Tables)	9 Months Ended
NET INCOME PER SHARE (Tables)	Sep. 30, 2021
Earnings Per Share [Abstract]
Reconciliation of the Weighted Average Number of Shares Outstanding Used in Calculating Diluted Net Income Per Share	A reconciliation of the weighted-average number of shares outstanding used in calculating diluted net income per share is as follows (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Weighted-average number of basic common shares outstanding 41,068 40,935 41,032 40,983 Weighted-average dilutive stock options, restricted stock units and performance share units 178 146 202 142 Assumed conversion of convertible senior notes 96 — 125 17 Weighted-average number of diluted common and common equivalent shares outstanding 41,342 41,081 41,359 41,142

INVESTMENTS (Tables)

INVESTMENTS (Tables)	9 Months Ended
INVESTMENTS (Tables)	Sep. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Investments by Major Security Type	The following table summarizes, by major security type, the Company's investments at September 30, 2021 (in millions): Cost Gross Gross Carrying Value Short-term investments: Debt securities: Trip.com Group convertible debt securities $ 525 $ — $ (3) $ 522 Long-term investments: Investments in private companies: Debt securities $ 200 $ 130 $ — $ 330 Equity securities 66 3 — 69 Other long-term investments: Equity securities 963 2,115 (194) 2,884 Total $ 1,229 $ 2,248 $ (194) $ 3,283 The following table summarizes, by major security type, the Company's investments at December 31, 2020 (in millions): Cost Gross Gross Unrealized Losses/Downward Adjustments Carrying Value Short-term investments: Debt securities: Trip.com Group convertible debt securities $ 500 $ 1 $ — $ 501 Long-term investments: Investments in private companies: Debt securities $ 200 $ — $ — $ 200 Equity securities 552 3 (100) 455 Other long-term investments: Debt securities: Trip.com Group convertible debt securities 25 — (1) 24 Equity securities 463 2,617 — 3,080 Total $ 1,240 $ 2,620 $ (101) $ 3,759

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	9 Months Ended
FAIR VALUE MEASUREMENTS (Tables)	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities Carried at Fair Value and Nonrecurring Fair Value Measurements	Financial assets and liabilities carried at fair value at September 30, 2021 and nonrecurring fair value measurements 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 $ 11,074 $ — $ — $ 11,074 Time deposits and certificates of deposit 41 — — 41 Short-term investments: Trip.com Group convertible debt securities — 522 — 522 Long-term investments: Investments in private companies: Debt securities — — 330 330 Other long-term investments: Equity securities 2,884 — — 2,884 Derivatives: Foreign currency exchange derivatives — 8 — 8 Total assets at fair value $ 13,999 $ 530 $ 330 $ 14,859 LIABILITIES: Foreign currency exchange derivatives $ — $ 11 $ — $ 11 Nonrecurring fair value measurements Investment in equity securities of a private company $ — $ 18 $ — $ 18 Financial assets and liabilities carried at fair value at December 31, 2020 and nonrecurring fair value measurements 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 $ 10,208 $ — $ — $ 10,208 Time deposits and certificates of deposit 32 — — 32 Short-term investments: Trip.com Group convertible debt securities — 501 — 501 Long-term investments: Investments in private companies: Debt securities — — 200 200 Other long-term investments: Trip.com Group convertible debt securities — 24 — 24 Equity securities 3,080 — — 3,080 Derivatives: Foreign currency exchange derivatives — 9 — 9 Total assets at fair value $ 13,320 $ 534 $ 200 $ 14,054 LIABILITIES: Foreign currency exchange derivatives $ — $ 7 $ — $ 7 Nonrecurring fair value measurements Investments in equity securities of private companies (1) $ — $ — $ 404 $ 404 Goodwill of the OpenTable and KAYAK reporting unit (2) — — 1,000 1,000 Total nonrecurring fair value measurements $ — $ — $ 1,404 $ 1,404 (1) At March 31, 2020, the investment in DiDi 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 the 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. At September 30, 2020, the goodwill was further written down to its estimated fair value of $1.0 billion, resulting in an additional impairment charge of $573 million (see Note 8).
Fair Value Adjustments for Debt Securities Measured using Significant Unobservable Inputs	The following table summarizes the fair value adjustments for debt securities measured using significant unobservable inputs (level 3) (in millions): For the Nine Months Ended September 30, 2021 2020 (1) Balance, beginning of year $ 200 $ 250 Unrealized gains included in accumulated other comprehensive loss (2) 130 — Balance, end of period $ 330 $ 250 (1) The Company recognized an unrealized loss of $20 million during the three months ended March 31, 2020 and an unrealized gain of $20 million during the three months ended June 30, 2020 related to the investment in Grab. (2) The unrealized gains are recorded in "Accumulated other comprehensive loss" in the Consolidated Balance Sheet.
Fair Value and the 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 September 30, 2021 and December 31, 2020 (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. September 30, 2021 December 31, 2020 Estimated fair value of derivative assets $ 8 $ 9 Estimated fair value of derivative liabilities $ 11 $ 7 Notional amount: Foreign currency purchases $ 867 $ 898 Foreign currency sales $ 1,559 $ 839 The effect of foreign currency exchange derivatives recorded in "Other income (expense), net" in the Unaudited Consolidated Statements of Operations for the three and nine months ended September 30, 2021 and 2020 is as follows (in millions): Three Months Ended September 30, Nine Months Ended 2021 2020 2021 2020 Losses on foreign currency exchange derivatives $ 10 $ — $ 18 $ 31

ACCOUNTS RECEIVABLE AND OTHER_2

ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS (Tables)	9 Months Ended
ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS (Tables)	Sep. 30, 2021
Receivables [Abstract]
Activity of the allowance for expected credit losses on receivables	The following table summarizes the activity of the allowance for expected credit losses on receivables (in millions): Nine Months Ended 2021 2020 Balance, beginning of year $ 166 $ 49 Provision charged to earnings 44 206 Write-offs and adjustments (96) (59) Foreign currency translation adjustments (4) 12 Balance, end of period $ 110 $ 208
Activity of the allowance for expected credit losses on prepayments to customers	The following table summarizes the activity of the allowance for expected credit losses on prepayments to customers (in millions): Nine Months Ended 2021 2020 Balance, beginning of year $ 55 $ 6 Provision charged to expense (2) 49 Write-offs and adjustments (3) (1) Balance, end of period $ 50 $ 54

GOODWILL, INTANGIBLE ASSETS A_2

GOODWILL, INTANGIBLE ASSETS AND OTHER LONG-LIVED ASSETS (Tables)	9 Months Ended
	Sep. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	The Company's intangible assets at September 30, 2021 and December 31, 2020 consist of the following (in millions): September 30, 2021 December 31, 2020 Gross Accumulated Net Gross Accumulated Net Amortization Supply and distribution agreements $ 1,114 $ (582) $ 532 $ 1,136 $ (552) $ 584 3 - 20 years Technology 174 (149) 25 174 (144) 30 2 - 7 years Internet domain names 41 (36) 5 44 (37) 7 5 - 20 years Trade names 1,816 (701) 1,115 1,824 (633) 1,191 4 - 20 years Other intangible assets 2 (2) — 2 (2) — Up to 15 years Total intangible assets $ 3,147 $ (1,470) $ 1,677 $ 3,180 $ (1,368) $ 1,812

DEBT (Tables)

DEBT (Tables)	9 Months Ended
DEBT (Tables)	Sep. 30, 2021
Debt Disclosure [Abstract]
Summary of Outstanding Debt	Outstanding debt at September 30, 2021 consists of the following (in millions): September 30, 2021 Outstanding Principal Amount Unamortized Debt Carrying Value Current liabilities: 0.8% (€1 billion) Senior Notes due March 2022 $ 1,159 $ (1) $ 1,158 Long-term debt: 2.15% (€750 million) Senior Notes due November 2022 $ 869 $ (1) $ 868 2.75% Senior Notes due March 2023 500 (1) 499 2.375% (€1 billion) Senior Notes due September 2024 1,159 (5) 1,154 3.65% Senior Notes due March 2025 500 (2) 498 0.1% (€950 million) Senior Notes due March 2025 1,101 (5) 1,096 0.75% Convertible Senior Notes due May 2025 863 (106) 757 3.6% Senior Notes due June 2026 1,000 (4) 996 1.8% (€1 billion) Senior Notes due March 2027 1,159 (3) 1,156 3.55% Senior Notes due March 2028 500 (2) 498 0.5% (€750 million) Senior Notes due March 2028 869 (5) 864 4.625% Senior Notes due April 2030 1,500 (10) 1,490 Total long-term debt $ 10,020 $ (144) $ 9,876 Outstanding debt at December 31, 2020 consists of the following (in millions): December 31, 2020 Outstanding Unamortized Debt Carrying Value Current Liabilities: 0.9% Convertible Senior Notes due September 2021 $ 1,000 $ (15) $ 985 Long-term debt: 0.8% (€1 billion) Senior Notes due March 2022 $ 1,223 $ (1) $ 1,222 2.15% (€750 million) Senior Notes due November 2022 919 (4) 915 2.75% Senior Notes due March 2023 500 (1) 499 2.375% (€1 billion) Senior Notes due September 2024 1,223 (7) 1,216 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 (128) 735 3.6% Senior Notes due June 2026 1,000 (4) 996 1.8% (€1 billion) Senior Notes due March 2027 1,223 (2) 1,221 4.5% Senior Notes due April 2027 750 (5) 745 3.55% Senior Notes due March 2028 500 (2) 498 4.625% Senior Notes due April 2030 1,500 (11) 1,489 Total long-term debt $ 11,201 $ (172) $ 11,029
Summary of Interest Expense	The following table summarizes the interest expenses and weighted-average effective interest rates related to the convertible senior notes (in millions, except for interest rates). The remaining period for amortization of debt discount and debt issuance costs is the period until the stated maturity date for the respective debt. For the Three Months Ended For the Nine Months Ended 2021 2020 2021 2020 Coupon interest expense $ 3 $ 4 $ 11 $ 11 Amortization of debt discount and debt issuance costs 12 13 36 42 Total interest expense $ 15 $ 17 $ 47 $ 53 Weighted-average effective interest rate 3.9 % 3.9 % 3.7 % 3.5 % The following table summarizes the interest expenses related to other senior notes (in millions): For the Three Months Ended For the Nine Months Ended 2021 2020 2021 2020 Coupon interest expense $ 60 $ 77 $ 198 $ 187 Amortization of debt discount and debt issuance costs 2 2 8 6 Total interest expense $ 62 $ 79 $ 206 $ 193
Schedule of other senior notes	The following table summarizes the information related to other senior notes outstanding at September 30, 2021: Other Senior Notes Date of Issuance Effective Interest Rate (1) Timing of Interest Payments 0.8% Senior Notes due March 2022 March 2017 0.94 % Annually in March 2.15% Senior Notes due November 2022 November 2015 2.27 % Annually in November 2.75% Senior Notes due March 2023 August 2017 2.88 % Semi-annually in March and September 2.375% Senior Notes due September 2024 September 2014 2.54 % Annually in September 3.65% Senior Notes due March 2025 March 2015 3.76 % Semi-annually in March and September 0.1% Senior Notes due March 2025 March 2021 0.30 % Annually in March 3.6% Senior Notes due June 2026 May 2016 3.70 % Semi-annually in June and December 1.8% Senior Notes due March 2027 March 2015 1.86 % Annually in March 3.55% Senior Notes due March 2028 August 2017 3.63 % Semi-annually in March and September 0.5% Senior Notes due March 2028 March 2021 0.63 % Annually in March 4.625% Senior Notes due April 2030 April 2020 4.72 % Semi-annually in April and October (1) Represents the coupon interest rate adjusted for deferred debt issuance costs, premiums or discounts existing at the origination of the debt.

TREASURY STOCK (Tables)

TREASURY STOCK (Tables)	9 Months Ended
TREASURY STOCK (Tables)	Sep. 30, 2021
Equity [Abstract]
Schedule of Stock Repurchase Activity	The following table summarizes the Company's stock repurchase activities during the three and nine months ended September 30, 2021 and 2020 (in millions, except for shares, which are reflected in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Shares Amount Shares Amount Shares Amount Shares Amount Authorized stock repurchase programs — $ — — $ — — $ — 601 $ 1,122 General authorization for shares withheld on stock award vesting 2 3 2 4 70 158 81 137 Total 2 $ 3 2 $ 4 70 $ 158 682 $ 1,259

CHANGES IN ACCUMULATED OTHER _2

CHANGES IN ACCUMULATED OTHER COMPREHENSIVE LOSS BY COMPONENT (Tables)	9 Months Ended
	Sep. 30, 2021
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Changes in the Balances of Accumulated Other Comprehensive Loss	The tables below present the changes in the balances of accumulated other comprehensive loss ("AOCI") by component for the three and nine months ended September 30, 2021 and 2020 (in millions): Foreign currency translation adjustments Unrealized losses on cash flow hedges (1) Net unrealized gains (losses) on available-for-sale securities Total AOCI, net of tax Foreign currency translation Net investment hedges (2) Total, net of tax Before tax Tax Total, net of tax Before tax Tax Total, net of tax Before tax Tax (3) Before tax Tax Three Months Ended September 30, 2021 Balance, June 30, 2021 $ (82) $ 50 $ (95) $ 16 $ (111) $ — $ — $ — $ 130 $ (62) $ 68 $ (43) Other comprehensive (loss) income ("OCI") before reclassifications (110) 10 93 (23) (30) — — — 1 — 1 (29) OCI for the period (110) 10 93 (23) (30) — — — 1 — 1 (29) Balance, September 30, 2021 $ (192) $ 60 $ (2) $ (7) $ (141) $ — $ — $ — $ 131 $ (62) $ 69 $ (72) Nine Months Ended September 30, 2021 Balance, December 31, 2020 $ 11 $ 47 $ (184) $ 37 $ (89) $ — $ — $ — $ 3 $ (32) $ (29) $ (118) OCI before reclassifications (203) 13 182 (44) (52) (15) 4 (11) 128 (30) 98 35 Amounts reclassified to (4) — — — — — 15 (4) 11 — — — 11 OCI for the period (203) 13 182 (44) (52) — — — 128 (30) 98 46 Balance, September 30, 2021 $ (192) $ 60 $ (2) $ (7) $ (141) $ — $ — $ — $ 131 $ (62) $ 69 $ (72) Foreign currency translation adjustments Unrealized losses on cash flow hedges (1) Net unrealized (losses) gains on available-for-sale securities Total AOCI, net of tax Foreign currency translation Net investment hedges (2) Total, net of tax Before tax Tax Total, net of tax Before tax Tax Total, net of tax Before tax Tax (3) Before tax Tax Three Months Ended September 30, 2020 Balance, June 30, 2020 $ (249) $ 58 $ 17 $ (10) $ (184) $ — $ — $ — $ (24) $ (25) $ (49) $ (233) OCI before reclassifications 99 (4) (69) 16 42 — — — (5) — (5) 37 OCI for the period 99 (4) (69) 16 42 — — — (5) — (5) 37 Balance, September 30, 2020 $ (150) $ 54 $ (52) $ 6 $ (142) $ — $ — $ — $ (29) $ (25) $ (54) $ (196) Nine Months Ended September 30, 2020 Balance, December 31, 2019 $ (186) $ 54 $ (2) $ (5) $ (139) $ — $ — $ — $ (7) $ (45) $ (52) $ (191) OCI before reclassifications 36 — (50) 11 (3) — — — (26) 6 (20) (23) Amounts reclassified to net income (4) — — — — — — — — 4 14 18 18 OCI for the period 36 — (50) 11 (3) — — — (22) 20 (2) (5) Balance, September 30, 2020 $ (150) $ 54 $ (52) $ 6 $ (142) $ — $ — $ — $ (29) $ (25) $ (54) $ (196) (1) Relates to the reverse treasury lock agreements entered in March 2021 that were designated as cash flow hedges and settled in April 2021 (see Note 6). (2) Net investment hedges balance at September 30, 2021 and earlier dates presented above, includes accumulated net losses from fair value adjustments of $35 million ($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 of the foreign currency exposure of the net investment in certain Euro functional currency subsidiaries (see Note 9). (3) 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"). (4) The reclassified losses before tax are included in "Other income (expense), net" and the related reclassified tax benefits 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 nine months ended September 30, 2020, the amounts reclassified to net income include 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. The tax expense is included in "Income tax expense" in the Unaudited Consolidated Statements of Operations.

OTHER INCOME (EXPENSE), NET (Ta

OTHER INCOME (EXPENSE), NET (Tables)	9 Months Ended
OTHER INCOME (EXPENSE), NET (Tables)	Sep. 30, 2021
Other Income and Expenses [Abstract]
Components of other income (expense), net	The components of other income (expense), net included the following (in millions): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Interest and dividend income $ 4 $ 5 $ 12 $ 49 Net (losses) gains on equity securities (1) (1,016) 733 (589) 1,261 Impairment of investment (1) — — — (100) Foreign currency transaction gains (losses) 45 (121) 92 (148) Loss on early extinguishment of debt (2) — — (242) — Other (3) — 1 (13) (4) Other income (expense), net $ (967) $ 618 $ (740) $ 1,058 (1) See Note 5 for additional information related to the net (losses) gains on equity securities and impairment of investment. (2) See Note 9 for additional information related to the loss on early extinguishment of debt. (3) The amount for the nine months ended September 30, 2021 includes losses on reverse treasury lock agreements which were designated as cash flow hedges (see Note 6).

OTHER (Tables)

OTHER (Tables)	9 Months Ended
OTHER (Tables)	Sep. 30, 2021
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): September 30, December 31, (Unaudited) As included in the Consolidated Balance Sheets: Cash and cash equivalents $ 11,643 $ 10,562 Restricted cash and cash equivalents included in "Other current assets" 20 20 Total cash and cash equivalents and restricted cash and cash equivalents as shown in the Unaudited Consolidated Statements of Cash Flows $ 11,663 $ 10,582

BASIS OF PRESENTATION (Details)

BASIS OF PRESENTATION (Details) $ in Millions, € in Billions	1 Months Ended			4 Months Ended	9 Months Ended
	Sep. 30, 2021USD ($)	Apr. 30, 2021USD ($)	Mar. 31, 2021EUR (€)	Sep. 30, 2021USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Mar. 31, 2020investment
Organization, Consolidation And Presentation Of Financial Statements [Line Items]
Number of Investments Impaired \| investment							1
Proceeds from the issuance of long-term debt					$ 2,015	$ 4,108
COVID-19
Organization, Consolidation And Presentation Of Financial Statements [Line Items]
Government Grant and other assistance benefit that was returned, cash paid				$ 107	$ 107
Senior Notes
Organization, Consolidation And Presentation Of Financial Statements [Line Items]
Proceeds from the issuance of long-term debt \| €			€ 1.7
Payments to redeem debt		$ 2,000
Payment to satisfy the aggregate principal amount and the conversion premium in excess of the principal amount	$ 1,100

REVENUE - Disaggregation of Rev

REVENUE - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 4,676	$ 2,640	$ 7,977	$ 5,558
Online accommodation reservation services \| Revenue Benchmark \| Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration risk percentage	89.00%	91.00%	87.00%	88.00%
Other sources of online travel reservation services and advertising and other revenues \| Revenue Benchmark \| Product Concentration Risk \| 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	$ 444	$ 214	$ 1,034	$ 604
The Netherlands
Disaggregation of Revenue [Line Items]
Revenues	3,955	2,231	6,367	4,352
Other
Disaggregation of Revenue [Line Items]
Revenues	$ 277	$ 195	$ 576	$ 602

REVENUE - Deferred Merchant Boo

REVENUE - Deferred Merchant Bookings and Deferred Revenue (Details) - Online travel reservation services - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Revenue, performance obligation, description of timing	one year
Deferred revenue balance, revenue recognized	$ 34
Deferred merchant bookings
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Deferred revenue for online travel reservation services	$ 163	$ 50

REVENUE - Loyalty and Other Inc

REVENUE - Loyalty and Other Incentive Programs (Details) - Accrued expenses and other current liabilities - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Loyalty Programs
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Liabilities for loyalty and other incentive program incentives	$ 13	$ 21
Other Incentive Programs
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Liabilities for loyalty and other incentive program incentives	$ 61	$ 60

REVENUE - Impact of COVID-19 (D

REVENUE - Impact of COVID-19 (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
(Increase) reduction in revenue for refunds paid or estimated to be payable due to the Impact of COVID-19	$ (21)	$ 42

STOCK-BASED EMPLOYEE COMPENSA_3

STOCK-BASED EMPLOYEE COMPENSATION - Narrative (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate grant-date fair value of performance share units and restricted stock units granted during the period	$ 22				$ 400
Aggregate fair value of performance share units and restricted stock units vested during the period	8				385
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense, reduction in expense for estimated probable outcome				$ 73
Performance Share Units \| 2018 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional stock-based compensation expense as a result of the modification to be recognized over the remaining requisite service period			$ 11
Performance Share Units \| 2018 and 2019 Grants \| Executive Officers
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional stock-based compensation expense as a result of the modification to be recognized over the remaining requisite service period		$ 40
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	520				$ 520
Total future compensation cost related to unvested share-based awards, expected period of recognition					2 years
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized estimated compensation expense, unvested share-based awards	$ 33				$ 33
Total future compensation cost related to unvested share-based awards, expected period of recognition					1 year 4 months 24 days

STOCK-BASED EMPLOYEE COMPENSA_4

STOCK-BASED EMPLOYEE COMPENSATION - Summary of Share-Based Compensation Activity (Details)	9 Months Ended
	Sep. 30, 2021$ / sharesshares
Share-Based Awards - Weighted Average Grant Date Fair Value
Performance share units awarded during the period where a grant date was not yet established.	12,251
Restricted Stock Units
Share-Based Awards - Shares
Unvested at December 31, 2020 (in shares)	305,959
Granted (in shares)	133,667
Vested (in shares)	(114,486)
Forfeited (in shares)	(39,382)
Unvested at September 30, 2021 (in shares)	285,758
Share-Based Awards - Weighted Average Grant Date Fair Value
Unvested at December 31, 2020 (in dollars per share) \| $ / shares	$ 1,697
Granted (in dollars per share) \| $ / shares	2,270
Vested (in dollars per share) \| $ / shares	1,793
Forfeited (in dollars per share) \| $ / shares	1,882
Unvested at September 30, 2021 (in dollars per share) \| $ / shares	$ 1,901
Performance Share Units
Share-Based Awards - Shares
Unvested at December 31, 2020 (in shares)	84,478
Granted (in shares)	42,173	[1]
Vested (in shares)	(55,426)
Performance share units adjustment (in shares)	44,346	[2]
Forfeited (in shares)	(7,248)
Unvested at September 30, 2021 (in shares)	108,323
Share-Based Awards - Weighted Average Grant Date Fair Value
Unvested at December 31, 2020 (in dollars per share) \| $ / shares	$ 1,930
Granted (in dollars per share) \| $ / shares	2,287	[1]
Vested (in dollars per share) \| $ / shares	1,999
Performance share units adjustment (in dollars per share) \| $ / shares	2,125	[2]
Forfeited (in dollars per share) \| $ / shares	1,792
Unvested at September 30, 2021 (in dollars per share) \| $ / shares	$ 2,123
Share-based payment award vesting period	3 years
Minimum \| Restricted Stock Units
Share-Based Awards - Weighted Average Grant Date Fair Value
Share-based payment award vesting period	1 year
Maximum \| Restricted Stock Units
Share-Based Awards - Weighted Average Grant Date Fair Value
Share-based payment award vesting period	3 years
2021 Grants \| Shares probable to be issued \| Performance Share Units
Share-Based Awards - Shares
Unvested at September 30, 2021 (in shares)	63,523	[3]
2021 Grants \| Shares not subject to the achievement of minimum performance thresholds \| Performance Share Units
Share-Based Awards - Shares
Unvested at September 30, 2021 (in shares)	28,198	[3]
2021 Grants \| Shares that could be issued if maximum performance thresholds are met \| Performance Share Units
Share-Based Awards - Shares
Unvested at September 30, 2021 (in shares)	63,523	[3]
2020 Grants \| Shares probable to be issued \| Performance Share Units
Share-Based Awards - Shares
Unvested at September 30, 2021 (in shares)	11,752
2020 Grants \| Shares not subject to the achievement of minimum performance thresholds \| Performance Share Units
Share-Based Awards - Shares
Unvested at September 30, 2021 (in shares)	0
2020 Grants \| Shares that could be issued if maximum performance thresholds are met \| Performance Share Units
Share-Based Awards - Shares
Unvested at September 30, 2021 (in shares)	18,080
2019 Grants \| Shares probable to be issued \| Performance Share Units
Share-Based Awards - Shares
Unvested at September 30, 2021 (in shares)	33,048
2019 Grants \| Shares not subject to the achievement of minimum performance thresholds \| Performance Share Units
Share-Based Awards - Shares
Unvested at September 30, 2021 (in shares)	33,048
2019 Grants \| Shares that could be issued if maximum performance thresholds are met \| Performance Share Units
Share-Based Awards - Shares
Unvested at September 30, 2021 (in shares)	61,669
Certain Performance Share Units 2021 Grants \| Performance Share Units
Share-Based Awards - Weighted Average Grant Date Fair Value
Share-based payment award vesting period	2 years
Certain Performance Share Units 2021 Grants \| Minimum \| Performance Share Units
Share-Based Awards - Weighted Average Grant Date Fair Value
Share-based payment award vesting period	1 year

[1]	Excludes 12,251 performance share units awarded during the nine months ended September 30, 2021 for which the grant date under ASC 718, Compensation - Stock Compensation , has not yet been established. Among other conditions, for the grant date to be established, a mutual understanding is required to be reached between the Company and the employee of the key terms and conditions of the award, including the performance targets. The performance targets for each of the annual performance periods under the award are set at the beginning of the respective year.
[2]	Probable outcome for performance-based awards is updated based upon changes in actual and forecasted operating results or expected achievement of performance goals, as applicable, and the impact of modifications.
[3]	Excludes performance share units awarded during the nine months ended September 30, 2021 for which the grant date under ASC 718 has not yet been established as disclosed above.

STOCK-BASED EMPLOYEE COMPENSA_5

STOCK-BASED EMPLOYEE COMPENSATION - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Weighted-average Remaining Contractual Term
Intrinsic value of options exercised during the period	$ 4	$ 14
Executive Officers
Number of Shares
Granted (in shares)		0
Stock Options
Number of Shares
Balance (in shares), December 31, 2020	152,746
Exercised (in shares)	(3,592)
Forfeited (in shares)	(12,846)
Balance (in shares), September 30, 2021	136,308		152,746
Exercisable (in shares), September 30, 2021	1,293
Weighted-average Exercise Price
Balance (in dollars per share), December 31, 2020	$ 1,401
Exercised (in dollars per share)	1,226
Forfeited (in dollars per share)	1,411
Balance (in dollars per share), September 30, 2021	1,405		$ 1,401
Exercisable (in dollars per share), September 30, 2021	$ 789
Aggregate Intrinsic Value
Balance	$ 132		$ 126
Exercisable	$ 2
Weighted-average Remaining Contractual Term
Balance	8 years 6 months		9 years 3 months 18 days
Exercisable	1 year 10 months 24 days
Stock option term	10 years

NET INCOME PER SHARE (Details)

NET INCOME PER SHARE (Details) - shares	3 Months Ended		9 Months Ended
NET INCOME PER SHARE (Details) - shares	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Weighted-average number of basic common shares outstanding (in shares)	41,068,000	40,935,000	41,032,000	40,983,000
Weighted-average dilutive stock options, restricted stock units and performance share units (in shares)	178,000	146,000	202,000	142,000
Assumed conversion of convertible senior notes (in shares)	96,000	0	125,000	17,000
Weighted-average number of diluted common and common equivalent shares outstanding (in shares)	41,342,000	41,081,000	41,359,000	41,142,000
Anti-dilutive potential common shares (in shares)		163,507	15,434	165,923

INVESTMENTS - Summary of Invest

INVESTMENTS - Summary of Investments by Major Security Type (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Long-term investments:
Carrying Value	$ 3,283	$ 3,759
Trip.com Group
Equity security investments with readily determinable fair value:
Cost			$ 655
Convertible Debt Securities \| Trip.com Group
Debt Securities, Available-for-sale [Abstract]
Cost	525
Short-term Investments \| Convertible Debt Securities \| Trip.com Group
Debt Securities, Available-for-sale [Abstract]
Cost	525	500
Gross Unrealized Gains/Upward Adjustments	0	1
Gross Unrealized Losses/Downward Adjustments	(3)	0
Carrying Value	522	501
Long-term investments
Long-term investments:
Cost	1,229	1,240
Gross Unrealized Gains /Upward Adjustments	2,248	2,620
Gross Unrealized Losses /Downward Adjustments	(194)	(101)
Carrying Value	3,283	3,759
Long-term investments \| Convertible Debt Securities \| Trip.com Group
Debt Securities, Available-for-sale [Abstract]
Cost		25
Gross Unrealized Gains/Upward Adjustments		0
Gross Unrealized Losses/Downward Adjustments		(1)
Carrying Value		24
Long-term investments \| Investments in private company debt securities
Debt Securities, Available-for-sale [Abstract]
Cost	200	200
Gross Unrealized Gains/Upward Adjustments	130	0
Gross Unrealized Losses/Downward Adjustments	0	0
Carrying Value	330	200
Long-term investments \| Investment in private company equity securities
Equity security investments in private companies:
Cost	66	552
Gross Unrealized Gains /Upward Adjustments	3	3
Gross Unrealized Losses /Downward Adjustments	0	(100)
Carrying Value	69	455
Long-term investments \| Equity securities
Equity security investments with readily determinable fair value:
Cost	963	463
Gross Unrealized Gains /Upward Adjustments	2,115	2,617
Gross Unrealized Losses /Downward Adjustments	(194)	0
Carrying Value	$ 2,884	$ 3,080

INVESTMENTS - Narrative (Detail

INVESTMENTS - Narrative (Details) $ in Millions		3 Months Ended				9 Months Ended		12 Months Ended
INVESTMENTS - Narrative (Details) $ in Millions		Dec. 31, 2021USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Schedule of Investments [Line Items]
Proceeds from sale and maturity of investments						$ 8	$ 2,997
Impairment of investment	[1]		$ 0	$ 0		0	100
Government and corporate debt securities
Schedule of Investments [Line Items]
Proceeds from sales and maturities of investments							2,200
Trip.com Group
Schedule of Investments [Line Items]
Cost of investment in equity securities with readily determinable fair values				655			655
Proceeds from sale and maturity of investments							525
Net realized loss on securities							201
Trip.com Group \| Convertible Debt Securities
Schedule of Investments [Line Items]
Amortized cost of available-for-sale debt securities			525			525
Meituan
Schedule of Investments [Line Items]
Payments to acquire other investments									$ 450
Unrealized (losses) gains on equity securities held			$ (772)	$ 727		$ (509)	$ 1,400
DiDi Global Inc.
Schedule of Investments [Line Items]
Payments to acquire other investments								$ 500
ADSs representing Class A ordinary share, ratio			0.25			0.25
Unrealized loss on securities held			$ 249			$ 94
Yanolja \| Subsequent Event \| Forecast
Schedule of Investments [Line Items]
Equity Securities without Readily Determinable Fair Value, Upward Price Adjustment, Annual Amount		$ 250
Long-term Investments \| Investment in private company equity securities
Schedule of Investments [Line Items]
Cost of investment without readily determinable fair values			66			66					$ 552
Investment in equity securities without readily determinable FV			69			69					455
Long-term Investments \| Trip.com Group \| Convertible Debt Securities
Schedule of Investments [Line Items]
Amortized cost of available-for-sale debt securities											25
Estimated fair value											24
Long-term Investments \| Meituan
Schedule of Investments [Line Items]
Carrying Value			2,600			2,600					3,100
Long-term Investments \| DiDi Global Inc.
Schedule of Investments [Line Items]
Carrying Value			306			306
Long-term Investments \| DiDi Global Inc. \| Investment in private company equity securities
Schedule of Investments [Line Items]
Impairment of investment					$ 100
Investment in equity securities without readily determinable FV					$ 400					$ 400	400
Long-term Investments \| Yanolja \| Investment in private company equity securities
Schedule of Investments [Line Items]
Cost of investment without readily determinable fair values			51			51					51
Long-term Investments \| Grab \| Redeemable Convertible Preferred Stock
Schedule of Investments [Line Items]
Amortized cost of available-for-sale debt securities			200			200					200
Estimated fair value			330			330					200
Short-term Investments \| Trip.com Group \| Convertible Debt Securities
Schedule of Investments [Line Items]
Amortized cost of available-for-sale debt securities			525			525					500
Estimated fair value			522			522					501
Short-term Investments \| Trip.com Group, Convertible Senior Notes, Issued September 2016 \| Convertible Debt Securities
Schedule of Investments [Line Items]
Amortized cost of available-for-sale debt securities			$ 25			$ 25
Term of available-for-sale debt securities			6 years			6 years
Short-term Investments \| Trip.com Group, Convertible Senior Notes, Issued December 2015 \| Convertible Debt Securities
Schedule of Investments [Line Items]
Amortized cost of available-for-sale debt securities			$ 500			$ 500					$ 500
Term of available-for-sale debt securities			10 years			10 years

[1]	See Note 5 for additional information related to the net (losses) gains on equity securities and impairment of investment.

FAIR VALUE MEASUREMENTS - Finan

FAIR VALUE MEASUREMENTS - Financial Assets and Liabilities Carried at Fair Value (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
LIABILITIES:
Impairment of investment	[1]	$ 0	$ 0		$ 0	$ 100
Goodwill		1,872			1,872		$ 1,895
Impairment of goodwill		0	573		0	1,062
OpenTable And KAYAK
LIABILITIES:
Goodwill			1,000	$ 1,500		$ 1,000
Impairment of goodwill			$ 573	489
DiDi Global Inc. \| Investment in private company equity securities \| Long-term Investments
LIABILITIES:
Impairment of investment				100
Recurring Basis
ASSETS:
Assets at fair value		14,859			14,859		14,054
Recurring Basis \| Money market fund investments \| Cash Equivalents and Restricted Cash Equivalents
ASSETS:
Assets at fair value		11,074			11,074		10,208
Recurring Basis \| Time deposits and certificates of deposit \| Cash Equivalents and Restricted Cash Equivalents
ASSETS:
Assets at fair value		41			41		32
Recurring Basis \| Investments in private company debt securities \| Long-term Investments
ASSETS:
Assets at fair value		330			330		200
Recurring Basis \| Equity securities \| Long-term Investments
ASSETS:
Assets at fair value		2,884			2,884		3,080
Recurring Basis \| Trip.com Group \| Convertible Debt Securities \| Short-term Investments
ASSETS:
Assets at fair value		522			522		501
Recurring Basis \| Trip.com Group \| Convertible Debt Securities \| Long-term Investments
ASSETS:
Assets at fair value							24
Recurring Basis \| Not Designated as Hedging Instrument \| Foreign currency exchange derivatives
ASSETS:
Assets at fair value		8			8		9
LIABILITIES:
Liabilities at fair value		11			11		7
Nonrecurring Basis
ASSETS:
Assets at fair value							1,404
Nonrecurring Basis \| Investment in private company equity securities \| Long-term Investments
ASSETS:
Assets at fair value		18			18		404	[2]
Nonrecurring Basis \| Goodwill \| OpenTable And KAYAK
ASSETS:
Assets at fair value	[3]						1,000
Nonrecurring Basis \| DiDi Global Inc. \| Investment in private company equity securities \| Long-term Investments
ASSETS:
Assets at fair value				$ 400
Level 1 \| Recurring Basis
ASSETS:
Assets at fair value		13,999			13,999		13,320
Level 1 \| Recurring Basis \| Money market fund investments \| Cash Equivalents and Restricted Cash Equivalents
ASSETS:
Assets at fair value		11,074			11,074		10,208
Level 1 \| Recurring Basis \| Time deposits and certificates of deposit \| Cash Equivalents and Restricted Cash Equivalents
ASSETS:
Assets at fair value		41			41		32
Level 1 \| Recurring Basis \| Investments in private company debt securities \| Long-term Investments
ASSETS:
Assets at fair value		0			0		0
Level 1 \| Recurring Basis \| Equity securities \| Long-term Investments
ASSETS:
Assets at fair value		2,884			2,884		3,080
Level 1 \| Recurring Basis \| Trip.com Group \| Convertible Debt Securities \| Short-term Investments
ASSETS:
Assets at fair value		0			0		0
Level 1 \| Recurring Basis \| Trip.com Group \| Convertible Debt Securities \| Long-term Investments
ASSETS:
Assets at fair value							0
Level 1 \| Recurring Basis \| Not Designated as Hedging Instrument \| Foreign currency exchange derivatives
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
Level 1 \| Nonrecurring Basis \| Investment in private company equity securities \| Long-term Investments
ASSETS:
Assets at fair value		0			0		0	[2]
Level 1 \| Nonrecurring Basis \| Goodwill \| OpenTable And KAYAK
ASSETS:
Assets at fair value	[3]						0
Level 2 \| Recurring Basis
ASSETS:
Assets at fair value		530			530		534
Level 2 \| Recurring Basis \| Money market fund investments \| Cash Equivalents and Restricted Cash Equivalents
ASSETS:
Assets at fair value		0			0		0
Level 2 \| Recurring Basis \| Time deposits and certificates of deposit \| Cash Equivalents and Restricted Cash Equivalents
ASSETS:
Assets at fair value		0			0		0
Level 2 \| Recurring Basis \| Investments in private company debt securities \| Long-term Investments
ASSETS:
Assets at fair value		0			0		0
Level 2 \| Recurring Basis \| Equity securities \| Long-term Investments
ASSETS:
Assets at fair value		0			0		0
Level 2 \| Recurring Basis \| Trip.com Group \| Convertible Debt Securities \| Short-term Investments
ASSETS:
Assets at fair value		522			522		501
Level 2 \| Recurring Basis \| Trip.com Group \| Convertible Debt Securities \| Long-term Investments
ASSETS:
Assets at fair value							24
Level 2 \| Recurring Basis \| Not Designated as Hedging Instrument \| Foreign currency exchange derivatives
ASSETS:
Assets at fair value		8			8		9
LIABILITIES:
Liabilities at fair value		11			11		7
Level 2 \| Nonrecurring Basis
ASSETS:
Assets at fair value							0
Level 2 \| Nonrecurring Basis \| Investment in private company equity securities \| Long-term Investments
ASSETS:
Assets at fair value		18			18		0	[2]
Level 2 \| Nonrecurring Basis \| Goodwill \| OpenTable And KAYAK
ASSETS:
Assets at fair value	[3]						0
Level 3 \| Recurring Basis
ASSETS:
Assets at fair value		330			330		200
Level 3 \| Recurring Basis \| Money market fund investments \| Cash Equivalents and Restricted Cash Equivalents
ASSETS:
Assets at fair value		0			0		0
Level 3 \| Recurring Basis \| Time deposits and certificates of deposit \| Cash Equivalents and Restricted Cash Equivalents
ASSETS:
Assets at fair value		0			0		0
Level 3 \| Recurring Basis \| Investments in private company debt securities \| Long-term Investments
ASSETS:
Assets at fair value		330			330		200
Level 3 \| Recurring Basis \| Equity securities \| Long-term Investments
ASSETS:
Assets at fair value		0			0		0
Level 3 \| Recurring Basis \| Trip.com Group \| Convertible Debt Securities \| Short-term Investments
ASSETS:
Assets at fair value		0			0		0
Level 3 \| Recurring Basis \| Trip.com Group \| Convertible Debt Securities \| Long-term Investments
ASSETS:
Assets at fair value							0
Level 3 \| Recurring Basis \| Not Designated as Hedging Instrument \| Foreign currency exchange derivatives
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							1,404
Level 3 \| Nonrecurring Basis \| Investment in private company equity securities \| Long-term Investments
ASSETS:
Assets at fair value		$ 0			$ 0		404	[2]
Level 3 \| Nonrecurring Basis \| Goodwill \| OpenTable And KAYAK
ASSETS:
Assets at fair value	[3]						$ 1,000

[1]	See Note 5 for additional information related to the net (losses) gains on equity securities and impairment of investment.
[2]	At March 31, 2020, the investment in DiDi was written down to its estimated fair value of $400 million, resulting in an impairment charge of $100 million (see Note 5).
[3]	At March 31, 2020, the goodwill of the 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. At September 30, 2020, the goodwill was further written down to its estimated fair value of $1.0 billion, resulting in an additional impairment charge of $573 million (see Note 8).

FAIR VALUE MEASUREMENTS - Rollf

FAIR VALUE MEASUREMENTS - Rollforward of Level 3 Fair Value Measurements (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Jun. 30, 2020	Mar. 31, 2020		Sep. 30, 2021	Sep. 30, 2020	[1]
Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year			$ 250	[1]	$ 200	$ 250
Unrealized gains included in accumulated other comprehensive loss	[2]				130	0
Balance, end of period					$ 330	$ 250
Grab \| Redeemable Convertible Preferred Stock \| Long-term Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Unrealized gain (loss) on debt securities		$ 20	$ (20)

[1]	The Company recognized an unrealized loss of $20 million during the three months ended March 31, 2020 and an unrealized gain of $20 million during the three months ended June 30, 2020 related to the investment in Grab.
[2]	The unrealized gains are recorded in "Accumulated other comprehensive loss" in the Consolidated Balance Sheet.

FAIR VALUE MEASUREMENTS - Narra

FAIR VALUE MEASUREMENTS - Narrative (Details) $ in Millions	9 Months Ended
FAIR VALUE MEASUREMENTS - Narrative (Details) $ in Millions	Sep. 30, 2021USD ($)	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Mar. 31, 2020USD ($)
Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	$ 14,859		$ 14,054
Level 3 \| Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	330		200
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	$ 69		455
Grab \| Redeemable Convertible Preferred Stock \| Relative Weighting \| Market Approach
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement inputs	0.70
Grab \| Redeemable Convertible Preferred Stock \| Relative Weighting \| Income Approach
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement inputs	0.30
Grab \| Redeemable Convertible Preferred Stock \| Volatility \| Market Approach
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement inputs	0.65
Grab \| Redeemable Convertible Preferred Stock \| Expected Term \| Market Approach
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Time to liquidity	3 months
Grab \| Redeemable Convertible Preferred Stock \| Expected Term \| Income Approach
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Time to liquidity	5 months
Grab \| Redeemable Convertible Preferred Stock \| Minimum \| Volatility \| Income Approach
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement inputs	0.60
Grab \| Redeemable Convertible Preferred Stock \| Minimum \| Weighted average cost of capital \| Income Approach
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement inputs	0.120
Grab \| Redeemable Convertible Preferred Stock \| Minimum \| EBITDA Multiple \| Income Approach
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement inputs	12
Grab \| Redeemable Convertible Preferred Stock \| Maximum \| Volatility \| Income Approach
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement inputs	0.70
Grab \| Redeemable Convertible Preferred Stock \| Maximum \| Weighted average cost of capital \| Income Approach
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement inputs	0.145
Grab \| Redeemable Convertible Preferred Stock \| Maximum \| EBITDA Multiple \| Income Approach
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement inputs	14
Grab \| Long-term Investments \| Redeemable Convertible Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost of available-for-sale debt securities	$ 200		200
Grab \| Long-term Investments \| Redeemable Convertible Preferred Stock \| Level 3 \| Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	330		200
DiDi Global Inc. \| 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	$ 400
Trip.com Group, Convertible Senior Notes, Issued September 2016 \| Short-term Investments \| 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

FAIR VALUE MEASUREMENTS - Notio

FAIR VALUE MEASUREMENTS - Notional Amount of Foreign Currency Exchange Derivatives (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended			9 Months Ended
	Apr. 30, 2021	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Losses on foreign currency exchange derivatives		$ 10		$ 0	$ 18	$ 31
Recurring Basis
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Assets at fair value		14,859			14,859		$ 14,054
Recurring Basis \| Level 2
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Assets at fair value		530			530		534
Foreign currency exchange derivatives \| Not Designated as Hedging Instrument \| Foreign currency purchases
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount		867			867		898
Foreign currency exchange derivatives \| Not Designated as Hedging Instrument \| Foreign currency sales
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount		1,559			1,559		839
Foreign currency exchange derivatives \| Not Designated as Hedging Instrument \| Recurring Basis
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Assets at fair value		8			8		9
Liabilities at fair value		11			11		7
Foreign currency exchange derivatives \| Not Designated as Hedging Instrument \| Recurring Basis \| Level 2
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Assets at fair value		8			8		9
Liabilities at fair value		$ 11			$ 11		$ 7
Reverse Treasury Lock \| Designated as Hedging Instrument \| Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount			$ 1,800
Unrealized losses			$ 15
Payments for reverse treasury lock agreements	$ 15

ACCOUNTS RECEIVABLE AND OTHER_3

ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables from customers	$ 1,300		$ 510
Receivables from marketing affiliates	40		32
Provision charged to earnings	44	$ 206
Revenue
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision charged to earnings	13	$ 32
Prepaid expenses, net
Accounts, Notes, Loans and Financing Receivable [Line Items]
Prepayments to customers	68		107
Other assets, net
Accounts, Notes, Loans and Financing Receivable [Line Items]
Prepayments to customers	$ 35		$ 45

ACCOUNTS RECEIVABLE AND OTHER_4

ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS - Summary of the Activity of the Allowance for Expected Credit Losses on Accounts Receivable (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of year	$ 166	$ 49
Provision charged to earnings	44	206
Write-offs and adjustments	(96)	(59)
Foreign currency translation adjustments	(4)	12
Balance, end of period	$ 110	$ 208

ACCOUNTS RECEIVABLE AND OTHER_5

ACCOUNTS RECEIVABLE AND OTHER FINANCIAL ASSETS - Summary of the Activity of the Allowance for Expected Credit Losses on Prepayments to Customers (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Contract With Customer, Asset, Prepayments To Customers, Allowance for Credit Loss [Abstract]
Balance, beginning of year	$ 55	$ 6
Provision charged to expense	(2)	49
Write-offs and adjustments	(3)	(1)
Balance, end of period	$ 50	$ 54

GOODWILL, INTANGIBLE ASSETS A_3

GOODWILL, INTANGIBLE ASSETS AND OTHER LONG-LIVED ASSETS - Goodwill (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Goodwill
Impairment of goodwill	$ 0	$ 573		$ 0	$ 1,062
Cumulative impairment charges	$ 2,000			$ 2,000		$ 2,000
OpenTable And KAYAK
Goodwill
Impairment of goodwill		$ 573	$ 489

GOODWILL, INTANGIBLE ASSETS A_4

GOODWILL, INTANGIBLE ASSETS AND OTHER LONG-LIVED ASSETS - Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Finite-lived intangible assets
Gross Carrying Amount	$ 3,147		$ 3,147		$ 3,180
Accumulated Amortization	(1,470)		(1,470)		(1,368)
Net Carrying Amount	1,677		1,677		1,812
Amortization expense	40	$ 41	122	$ 126
Supply and distribution agreements
Finite-lived intangible assets
Gross Carrying Amount	1,114		1,114		1,136
Accumulated Amortization	(582)		(582)		(552)
Net Carrying Amount	532		$ 532		584
Supply and distribution agreements \| Minimum
Finite-lived intangible assets
Amortization Period			3 years
Supply and distribution agreements \| Maximum
Finite-lived intangible assets
Amortization Period			20 years
Technology
Finite-lived intangible assets
Gross Carrying Amount	174		$ 174		174
Accumulated Amortization	(149)		(149)		(144)
Net Carrying Amount	25		$ 25		30
Technology \| Minimum
Finite-lived intangible assets
Amortization Period			2 years
Technology \| Maximum
Finite-lived intangible assets
Amortization Period			7 years
Internet domain names
Finite-lived intangible assets
Gross Carrying Amount	41		$ 41		44
Accumulated Amortization	(36)		(36)		(37)
Net Carrying Amount	5		$ 5		7
Internet domain names \| Minimum
Finite-lived intangible assets
Amortization Period			5 years
Internet domain names \| Maximum
Finite-lived intangible assets
Amortization Period			20 years
Trade names
Finite-lived intangible assets
Gross Carrying Amount	1,816		$ 1,816		1,824
Accumulated Amortization	(701)		(701)		(633)
Net Carrying Amount	1,115		$ 1,115		1,191
Trade names \| Minimum
Finite-lived intangible assets
Amortization Period			4 years
Trade names \| Maximum
Finite-lived intangible assets
Amortization Period			20 years
Other intangible assets
Finite-lived intangible assets
Gross Carrying Amount	2		$ 2		2
Accumulated Amortization	(2)		(2)		(2)
Net Carrying Amount	$ 0		$ 0		$ 0
Other intangible assets \| Maximum
Finite-lived intangible assets
Amortization Period			15 years

DEBT - Narrative (Details)

DEBT - Narrative (Details) $ / shares in Units, € in Millions		1 Months Ended					3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2021USD ($)	Apr. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Apr. 30, 2020USD ($)day$ / shares	Aug. 31, 2019USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)	Sep. 30, 2021EUR (€)	Mar. 31, 2021EUR (€)	Aug. 31, 2014USD ($)	May 31, 2013USD ($)
Debt Instrument
Payments of debt issuance costs									$ 10,000,000	$ 38,000,000
Loss on early extinguishment of debt	[1]						$ 0	$ 0	242,000,000	0
Level 2
Debt Instrument
Estimated market value of outstanding debt		$ 12,300,000,000					$ 12,300,000,000		$ 12,300,000,000		$ 14,000,000,000
Convertible Debt \| 0.9% Convertible Senior Notes due September 2021
Debt Instrument
Aggregate principal amount														$ 1,000,000,000
Stated interest rate														0.90%
Payments related to principal amount		1,000,000,000
Payments related to conversion value in excess of the principal amount of senior notes		$ 86,000,000
Effective interest rate at debt origination														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
Convertible Debt \| 0.75% Convertible Senior Notes due May 2025
Debt Instrument
Aggregate principal amount					$ 863,000,000
Stated interest rate		0.75%			0.75%		0.75%		0.75%		0.75%	0.75%
Payments of debt issuance costs											$ 19,000,000
Conversion price \| $ / shares					$ 1,886.44
Ratio of closing share price to conversion price as a condition for conversion of the convertible notes, minimum (Percentage)					130.00%
If-converted value in excess of principal									$ 215,000,000
Effective interest rate at debt origination					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
Aggregate principal amount		$ 863,000,000					$ 863,000,000		863,000,000		863,000,000
Convertible Debt \| 0.35% Convertible Senior Notes due June 2020
Debt Instrument
Aggregate principal amount															$ 1,000,000,000
Stated interest rate															0.35%
Payments related to principal amount				$ 1,000,000,000
Payments related to conversion value in excess of the principal amount of senior notes				$ 245,000,000
Senior Notes
Debt Instrument
Payments to redeem debt			$ 2,000,000,000
Carrying value of long-term debt		$ 10,300,000,000					$ 10,300,000,000		$ 10,300,000,000		$ 10,300,000,000
Senior Notes \| 0.1% (€950 million) Senior Notes due March 2025
Debt Instrument
Aggregate principal amount \| €												€ 950
Stated interest rate		0.10%					0.10%		0.10%			0.10%	0.10%
Effective interest rate at debt origination	[2]												0.30%
Aggregate principal amount		$ 1,101,000,000					$ 1,101,000,000		$ 1,101,000,000				€ 950
Senior Notes \| 0.5% (€750 million) Senior Notes due March 2028
Debt Instrument
Aggregate principal amount \| €												€ 750
Stated interest rate		0.50%					0.50%		0.50%			0.50%	0.50%
Effective interest rate at debt origination	[2]												0.63%
Aggregate principal amount		$ 869,000,000					$ 869,000,000		$ 869,000,000				€ 750
Senior Notes \| 4.1% Senior Notes due April 2025 and 4.5% Senior Notes due April 2027
Debt Instrument
Loss on early extinguishment of debt									242,000,000
Senior Notes \| 4.1% Senior Notes due April 2025
Debt Instrument
Stated interest rate											4.10%
Aggregate principal amount											$ 1,000,000,000
Payments to redeem debt			1,100,000,000
Senior Notes \| 4.5% Senior Notes due April 2027
Debt Instrument
Stated interest rate											4.50%
Aggregate principal amount											$ 750,000,000
Payments to redeem debt			$ 868,000,000
Minimum \| Euro-Denominated Debt \| Designated as Hedging Instrument
Debt Instrument
Carrying value of the portions of euro-denominated debt designated as a net investment hedge									2,500,000,000	1,800,000,000
Minimum \| Convertible Debt \| 0.75% Convertible Senior Notes due May 2025
Debt Instrument
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) \| day					20
Additional payment to debt holder, settled In shares, aggregate value					$ 0
Maximum \| Euro-Denominated Debt \| Designated as Hedging Instrument
Debt Instrument
Carrying value of the portions of euro-denominated debt designated as a net investment hedge									4,300,000,000	$ 3,200,000,000
Maximum \| Convertible Debt \| 0.75% Convertible Senior Notes due May 2025
Debt Instrument
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) \| day					30
Additional payment to debt holder, settled In shares, aggregate value					$ 235,000,000
Revolving Credit Facility
Debt Instrument
Revolving credit facility, maximum borrowing capacity						$ 2,000,000,000
Revolving credit facility, term						5 years
Line of credit, current		0					0		0		0
Debt instrument, covenant, minimum liquidity amount											4,500,000,000
Debt instrument, covenant, pro forma liquidity required for distribution and share repurchases											6,000,000,000
Revolving Credit Facility \| Minimum
Debt Instrument
Commitment fee rate						0.07%
Revolving Credit Facility \| Maximum
Debt Instrument
Commitment fee rate						0.20%
Revolving Credit Facility \| Rate 1 \| Minimum \| London Interbank Offered Rate (LIBOR)
Debt Instrument
Reference rate						0.00%
Basis spread on variable rate						0.875%
Revolving Credit Facility \| Rate 1 \| Maximum \| London Interbank Offered Rate (LIBOR)
Debt Instrument
Basis spread on variable rate						1.50%
Revolving Credit Facility \| Rate 2B \| Federal Funds Purchased
Debt Instrument
Basis spread on variable rate						0.50%
Revolving Credit Facility \| Rate 2C \| One Month LIBOR
Debt Instrument
Basis spread on variable rate						1.00%
Revolving Credit Facility \| Rate 2C \| Minimum
Debt Instrument
Basis spread on variable rate						0.00%
Revolving Credit Facility \| Rate 2C \| Minimum \| One Month LIBOR
Debt Instrument
Reference rate						0.00%
Revolving Credit Facility \| Rate 2C \| Maximum
Debt Instrument
Basis spread on variable rate						0.50%
Letter of Credit
Debt Instrument
Revolving credit facility, maximum borrowing capacity						$ 80,000,000
Letters of credit issued		$ 4,000,000					$ 4,000,000		$ 4,000,000		$ 4,000,000
Swingline Loans
Debt Instrument
Revolving credit facility, maximum borrowing capacity						$ 100,000,000

[1]	See Note 9 for additional information related to the loss on early extinguishment of debt.
[2]	Represents the coupon interest rate adjusted for deferred debt issuance costs, premiums or discounts existing at the origination of the debt.

DEBT - Schedule of Outstanding

DEBT - Schedule of Outstanding Debt (Details) € in Millions, $ in Millions	Sep. 30, 2021USD ($)	Sep. 30, 2021EUR (€)	Mar. 31, 2021EUR (€)	Dec. 31, 2020USD ($)	Dec. 31, 2020EUR (€)	Apr. 30, 2020USD ($)	Aug. 31, 2017	Mar. 31, 2017	May 31, 2016	Nov. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Aug. 31, 2014USD ($)
Current Liabilities:
Carrying Value	$ 1,158			$ 985
Long-term debt:
Carrying Value	9,876			11,029
Total long-term debt
Long-term debt:
Outstanding Principal Amount	10,020			11,201
Unamortized Debt Discount and Debt Issuance Cost	(144)			(172)
Carrying Value	9,876			11,029
0.9% Convertible Senior Notes due September 2021 \| Convertible Debt
Long-term debt:
Aggregate principal amount													$ 1,000
Stated interest rate													0.90%
0.9% Convertible Senior Notes due September 2021 \| Convertible Debt
Current Liabilities:
Carrying Value				985
Long-term debt:
Outstanding Principal Amount				1,000
Unamortized Debt Discount and Debt Issuance Cost				$ (15)
Stated interest rate				0.90%	0.90%
0.8% (€1 billion) Senior Notes due March 2022 \| Senior Notes
Long-term debt:
Outstanding Principal Amount				$ 1,223
Unamortized Debt Discount and Debt Issuance Cost				(1)
Carrying Value				$ 1,222
Aggregate principal amount \| €					€ 1,000
Stated interest rate				0.80%	0.80%			0.80%
0.8% (€1 billion) Senior Notes due March 2022 \| Senior Notes
Current Liabilities:
Carrying Value	1,158
Long-term debt:
Outstanding Principal Amount	1,159
Unamortized Debt Discount and Debt Issuance Cost	$ (1)
Aggregate principal amount \| €		€ 1,000
Stated interest rate	0.80%	0.80%
2.15% (€750 million) Senior Notes due November 2022 \| Senior Notes
Long-term debt:
Outstanding Principal Amount	$ 869			$ 919
Unamortized Debt Discount and Debt Issuance Cost	(1)			(4)
Carrying Value	$ 868			$ 915
Aggregate principal amount \| €		€ 750			€ 750
Stated interest rate	2.15%	2.15%		2.15%	2.15%					2.15%
2.75% Senior Notes due March 2023 \| Senior Notes
Long-term debt:
Outstanding Principal Amount	$ 500			$ 500
Unamortized Debt Discount and Debt Issuance Cost	(1)			(1)
Carrying Value	$ 499			$ 499
Stated interest rate	2.75%	2.75%		2.75%	2.75%		2.75%
2.375% (€1 billion) Senior Notes due September 2024 \| Senior Notes
Long-term debt:
Outstanding Principal Amount	$ 1,159			$ 1,223
Unamortized Debt Discount and Debt Issuance Cost	(5)			(7)
Carrying Value	$ 1,154			$ 1,216
Aggregate principal amount \| €		€ 1,000			€ 1,000
Stated interest rate	2.375%	2.375%		2.375%	2.375%							2.375%
3.65% Senior Notes due March 2025 \| Senior Notes
Long-term debt:
Outstanding Principal Amount	$ 500			$ 500
Unamortized Debt Discount and Debt Issuance Cost	(2)			(2)
Carrying Value	$ 498			$ 498
Stated interest rate	3.65%	3.65%		3.65%	3.65%						3.65%
0.1% (€950 million) Senior Notes due March 2025 \| Senior Notes
Long-term debt:
Outstanding Principal Amount	$ 1,101		€ 950
Unamortized Debt Discount and Debt Issuance Cost	(5)
Carrying Value	$ 1,096
Aggregate principal amount \| €		€ 950
Stated interest rate	0.10%	0.10%	0.10%
4.1% Senior Notes due April 2025 \| Senior Notes
Long-term debt:
Outstanding Principal Amount				$ 1,000
Unamortized Debt Discount and Debt Issuance Cost				(5)
Carrying Value				$ 995
Stated interest rate				4.10%	4.10%
0.75% Convertible Senior Notes due May 2025 \| Convertible Debt
Long-term debt:
Outstanding Principal Amount	$ 863			$ 863
Unamortized Debt Discount and Debt Issuance Cost	(106)			(128)
Carrying Value	$ 757			$ 735
Aggregate principal amount						$ 863
Stated interest rate	0.75%	0.75%		0.75%	0.75%	0.75%
3.6% Senior Notes due June 2026 \| Senior Notes
Long-term debt:
Outstanding Principal Amount	$ 1,000			$ 1,000
Unamortized Debt Discount and Debt Issuance Cost	(4)			(4)
Carrying Value	$ 996			$ 996
Stated interest rate	3.60%	3.60%		3.60%	3.60%				3.60%
1.8% (€1 billion) Senior Notes due March 2027 \| Senior Notes
Long-term debt:
Outstanding Principal Amount	$ 1,159			$ 1,223
Unamortized Debt Discount and Debt Issuance Cost	(3)			(2)
Carrying Value	$ 1,156			$ 1,221
Aggregate principal amount \| €		€ 1,000			€ 1,000
Stated interest rate	1.80%	1.80%		1.80%	1.80%						1.80%
4.5% Senior Notes due April 2027 \| Senior Notes
Long-term debt:
Outstanding Principal Amount				$ 750
Unamortized Debt Discount and Debt Issuance Cost				(5)
Carrying Value				$ 745
Stated interest rate				4.50%	4.50%
3.55% Senior Notes due March 2028 \| Senior Notes
Long-term debt:
Outstanding Principal Amount	$ 500			$ 500
Unamortized Debt Discount and Debt Issuance Cost	(2)			(2)
Carrying Value	$ 498			$ 498
Stated interest rate	3.55%	3.55%		3.55%	3.55%		3.55%
0.5% (€750 million) Senior Notes due March 2028 \| Senior Notes
Long-term debt:
Outstanding Principal Amount	$ 869		€ 750
Unamortized Debt Discount and Debt Issuance Cost	(5)
Carrying Value	$ 864
Aggregate principal amount \| €		€ 750
Stated interest rate	0.50%	0.50%	0.50%
4.625% Senior Notes due April 2030 \| Senior Notes
Long-term debt:
Outstanding Principal Amount	$ 1,500			$ 1,500
Unamortized Debt Discount and Debt Issuance Cost	(10)			(11)
Carrying Value	$ 1,490			$ 1,489
Stated interest rate	4.625%	4.625%		4.625%	4.625%	4.625%

DEBT - Summary of Interest Expe

DEBT - Summary of Interest Expenses and Weighted-Average Effective Interest Rates Related To Convertible Senior Notes and Other Senior Notes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Instrument
Amortization of debt discount and debt issuance costs			$ 44	$ 48
Convertible Debt
Debt Instrument
Coupon interest expense	$ 3	$ 4	11	11
Amortization of debt discount and debt issuance costs	12	13	36	42
Total interest expense	$ 15	$ 17	$ 47	$ 53
Weighted-average effective interest rate	3.90%	3.90%	3.70%	3.50%
Senior Notes
Debt Instrument
Coupon interest expense	$ 60	$ 77	$ 198	$ 187
Amortization of debt discount and debt issuance costs	2	2	8	6
Total interest expense	$ 62	$ 79	$ 206	$ 193

DEBT - Summary of Information R

DEBT - Summary of Information Related to Other Senior Notes Outstanding (Details) - Senior Notes - USD ($) $ in Billions		Sep. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Apr. 30, 2020	Aug. 31, 2017	Mar. 31, 2017	May 31, 2016	Nov. 30, 2015	Mar. 31, 2015	Sep. 30, 2014
Debt Instrument
Carrying value of long-term debt		$ 10.3		$ 10.3
0.8% (€1 billion) Senior Notes due March 2022
Debt Instrument
Stated interest rate				0.80%			0.80%
Effective interest rate	[1]						0.94%
2.15% (€750 million) Senior Notes due November 2022
Debt Instrument
Stated interest rate		2.15%		2.15%					2.15%
Effective interest rate	[1]								2.27%
2.75% Senior Notes due March 2023
Debt Instrument
Stated interest rate		2.75%		2.75%		2.75%
Effective interest rate	[1]					2.88%
2.375% (€1 billion) Senior Notes due September 2024
Debt Instrument
Stated interest rate		2.375%		2.375%							2.375%
Effective interest rate	[1]										2.54%
3.65% Senior Notes due March 2025
Debt Instrument
Stated interest rate		3.65%		3.65%						3.65%
Effective interest rate	[1]									3.76%
0.1% (€950 million) Senior Notes due March 2025
Debt Instrument
Stated interest rate		0.10%	0.10%
Effective interest rate	[1]		0.30%
3.6% Senior Notes due June 2026
Debt Instrument
Stated interest rate		3.60%		3.60%				3.60%
Effective interest rate	[1]							3.70%
1.8% (€1 billion) Senior Notes due March 2027
Debt Instrument
Stated interest rate		1.80%		1.80%						1.80%
Effective interest rate	[1]									1.86%
3.55% Senior Notes due March 2028
Debt Instrument
Stated interest rate		3.55%		3.55%		3.55%
Effective interest rate	[1]					3.63%
0.5% (€750 million) Senior Notes due March 2028
Debt Instrument
Stated interest rate		0.50%	0.50%
Effective interest rate	[1]		0.63%
4.625% Senior Notes due April 2030
Debt Instrument
Stated interest rate		4.625%		4.625%	4.625%
Effective interest rate	[1]				4.72%

[1]	Represents the coupon interest rate adjusted for deferred debt issuance costs, premiums or discounts existing at the origination of the debt.

TREASURY STOCK (Details)

TREASURY STOCK (Details) - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
TREASURY STOCK (Details) - USD ($) shares in Thousands	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Equity, Class of Treasury Stock [Line Items]
Authorized stock repurchase programs (in shares)	2	2	70	682
Authorized stock repurchase programs	$ 3,000,000	$ 4,000,000	$ 158,000,000	$ 1,259,000,000
General authorization for shares withheld on stock award vesting (in shares)	2	2	70	81
General authorization for shares withheld on stock award vesting	$ 3,000,000	$ 4,000,000	$ 158,000,000	$ 137,000,000
Payments related to tax withholding for share-based compensation			159,000,000	$ 137,000,000
2019 Share Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Remaining authorization to repurchase common stock	$ 10,400,000,000		$ 10,400,000,000		$ 10,400,000,000
Amount of common stock repurchases authorized						$ 15,000,000,000
Common Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Authorized stock repurchase programs (in shares)	0	0	0	601
Authorized stock repurchase programs	$ 0	$ 0	$ 0	$ 1,122,000,000

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
INCOME TAXES (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Income Tax Contingency [Line Items]
Effective tax rate, percent	20.50%	4.10%	15.80%	30.40%
Federal statutory tax rate, percent			21.00%	21.00%
Unrecognized tax benefits	$ 97		$ 97		$ 84
Unrecognized tax benefits, income tax penalties and interest accrued	$ 31		$ 31		$ 31
Tax and Customs Administration, Netherlands
Income Tax Contingency [Line Items]
Federal statutory tax rate, percent			25.00%
Effective income tax rate at innovation box tax rate, percent			9.00%	7.00%

CHANGES IN ACCUMULATED OTHER _3

CHANGES IN ACCUMULATED OTHER COMPREHENSIVE LOSS BY COMPONENT (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021		Sep. 30, 2020	May 31, 2020
Total AOCI, net of tax
Balance		$ 4,799	$ 3,999	$ 4,893		$ 5,933
OCI, before reclassifications, net of tax		(29)	37	35		(23)
Amounts reclassified to net income, net of tax	[1]			11		18
Total other comprehensive (loss) income, net of tax		(29)	37	46		(5)
Balance		5,545	4,913	5,545		4,913
Trip.com Group Note Due 2020 \| Convertible Debt Securities
Total AOCI, net of tax
Amortized cost of available-for-sale debt securities							$ 250
Total AOCI
Total AOCI, net of tax
Balance		(43)	(233)	(118)		(191)
Balance		(72)	(196)	(72)		(196)
Foreign currency translation adjustments
Total AOCI, net of tax
Balance		(111)	(184)	(89)		(139)
OCI, before reclassifications, net of tax		(30)	42	(52)		(3)
Amounts reclassified to net income, net of tax	[1]			0	[2]	0
Total other comprehensive (loss) income, net of tax		(30)	42	(52)		(3)
Balance		(141)	(142)	(141)		(142)
Foreign currency translation adjustments \| Net Investment Hedging \| Foreign Currency Forward
Before tax
Balance		(53)	(53)	(53)		(53)
Balance		(53)	(53)	(53)		(53)
Total AOCI, net of tax
Balance		(35)	(35)	(35)		(35)
Balance		(35)	(35)	(35)		(35)
Foreign currency translation
Before tax
Balance		(82)	(249)	11		(186)
OCI before reclassifications, before tax		(110)	99	(203)		36
Amounts reclassified to net income, before tax	[1]			0		0
OCI after reclassifications, before tax		(110)	99	(203)		36
Balance		(192)	(150)	(192)		(150)
Tax (expense) benefit
Balance	[3]	50	58	47		54
OCI before reclassifications, tax	[3]	10	(4)	13		0
Amounts reclassified to net income, tax	[1],[3]			0		0
OCI after reclassifications, tax	[3]	10	(4)	13		0
Balance	[3]	60	54	60		54
Net Investment Hedges
Before tax
Balance	[2]	(95)	17	(184)		(2)
OCI before reclassifications, before tax	[2]	93	(69)	182		(50)
Amounts reclassified to net income, before tax	[1],[2]			0		0
OCI after reclassifications, before tax	[2]	93	(69)	182		(50)
Balance	[2]	(2)	(52)	(2)		(52)
Tax (expense) benefit
Balance	[2]	16	(10)	37		(5)
OCI before reclassifications, tax	[2]	(23)	16	(44)		11
Amounts reclassified to net income, tax	[1],[2]			0		0
OCI after reclassifications, tax	[2]	(23)	16	(44)		11
Balance	[2]	(7)	6	(7)		6
Unrealized losses on cash flow hedges
Before tax
Balance	[4]	0	0	0		0
OCI before reclassifications, before tax	[4]	0	0	(15)		0
Amounts reclassified to net income, before tax	[1],[4]			15		0
OCI after reclassifications, before tax	[4]	0	0	0		0
Balance	[4]	0	0	0		0
Tax (expense) benefit
Balance	[4]	0	0	0		0
OCI before reclassifications, tax	[4]	0	0	4		0
Amounts reclassified to net income, tax	[1],[4]			(4)		0
OCI after reclassifications, tax	[4]	0	0	0		0
Balance	[4]	0	0	0		0
Total AOCI, net of tax
Balance	[4]	0	0	0		0
OCI, before reclassifications, net of tax	[4]	0	0	(11)		0
Amounts reclassified to net income, net of tax	[1],[4]			11		0
Total other comprehensive (loss) income, net of tax	[4]	0	0	0		0
Balance	[4]	0	0	0		0
Net unrealized gains (losses) on available-for-sale securities
Before tax
Balance		130	(24)	3		(7)
OCI before reclassifications, before tax		1	(5)	128		(26)
Amounts reclassified to net income, before tax	[1]			0		4
OCI after reclassifications, before tax		1	(5)	128		(22)
Balance		131	(29)	131		(29)
Tax (expense) benefit
Balance		(62)	(25)	(32)		(45)
OCI before reclassifications, tax		0	0	(30)		6
Amounts reclassified to net income, tax	[1]			0		14
OCI after reclassifications, tax		0	0	(30)		20
Balance		(62)	(25)	(62)		(25)
Total AOCI, net of tax
Balance		68	(49)	(29)		(52)
OCI, before reclassifications, net of tax		1	(5)	98		(20)
Amounts reclassified to net income, net of tax	[1]			0		18
Total other comprehensive (loss) income, net of tax		1	(5)	98		(2)
Balance		$ 69	$ (54)	$ 69		(54)
Net unrealized gains (losses) on available-for-sale securities \| Trip.com Group Note Due 2020 \| Convertible Debt Securities
Tax (expense) benefit
Amounts reclassified to net income, tax						$ 15

[1]	The reclassified losses before tax are included in "Other income (expense), net" and the related reclassified tax benefits 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 nine months ended September 30, 2020, the amounts reclassified to net income include 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. The tax expense is included in "Income tax expense" in the Unaudited Consolidated Statements of Operations.
[2]	Net investment hedges balance at September 30, 2021 and earlier dates presented above, includes accumulated net losses from fair value adjustments of $35 million ($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 of the foreign currency exposure of the net investment in certain Euro functional currency subsidiaries (see Note 9).
[3]	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").
[4]	Relates to the reverse treasury lock agreements entered in March 2021 that were designated as cash flow hedges and settled in April 2021 (see Note 6).

COMMITMENTS AND CONTINGENCIES (

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

1 Months Ended

3 Months Ended

9 Months Ended

Oct. 31, 2021USD ($)

Sep. 30, 2021USD ($)

Sep. 30, 2021EUR (€)

Aug. 31, 2021USD ($)

Aug. 31, 2021EUR (€)

Jun. 30, 2021USD ($)

Jun. 30, 2021EUR (€)

Mar. 31, 2021USD ($)

Mar. 31, 2021EUR (€)

Dec. 31, 2019USD ($)

Dec. 31, 2019EUR (€)

Jan. 31, 2019USD ($)

Jan. 31, 2019EUR (€)

Dec. 31, 2018USD ($)

Dec. 31, 2018EUR (€)

Sep. 30, 2016USD ($)

Sep. 30, 2016EUR (€)

Dec. 31, 2015USD ($)

Dec. 31, 2015EUR (€)

Mar. 31, 2021USD ($)

Mar. 31, 2021EUR (€)

Sep. 30, 2021USD ($)

Sep. 30, 2021EUR (€)

Sep. 30, 2021TRY (₺)

Sep. 30, 2021EUR (€)

Sep. 30, 2021GBP (£)

Dec. 31, 2020USD ($)

Dec. 31, 2020EUR (€)

Sep. 30, 2020USD ($)

Sep. 30, 2020EUR (€)

Sep. 30, 2016EUR (€)

Commitments and Contingencies

Unrecognized tax benefits

$ 97

$ 84

Booking.com | Headquarters

Commitments and Contingencies

Contractual obligation

$ 313

€ 22

€ 270

Acquisition of land use rights

$ 48

€ 43

Booking.com | Headquarters | Headquarters Vendors

Commitments and Contingencies

Contractual obligation

Booking.com | Headquarters | Ground Lease

Commitments and Contingencies

Remaining lease payments

$ 79

€ 69

Rentalcars.com | Headquarters | Manchester, England

Commitments and Contingencies

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

13 years

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

Commitments and Contingencies

Contractual obligation

$ 71

£ 52

Potential Fine under Contractual Parity Agreement

Commitments and Contingencies

Accruals for loss contingencies

€ 14

€ 18

French Tax Audit

Commitments and Contingencies

Unrecognized tax benefits

Estimated reasonably possible loss in excess of amount accrued

$ 23

€ 20

French Tax Audit | Tax Year 2013

Commitments and Contingencies

Assessed taxes including interest and penalties

$ 81

€ 70

French Tax Audit | Tax Years 2006 Through 2012

Commitments and Contingencies

Assessed taxes including interest and penalties

$ 403

€ 356

Payment required to appeal a litigation matter or avoid collection enforcement

$ 403

€ 356

French Tax Assessment, transfer taxes | Tax Years 2011 Through 2015

Commitments and Contingencies

Assessed taxes including interest and penalties

Italian Tax Audit

Commitments and Contingencies

Expected required prepayment deposit or bank guarantees

$ 70

€ 60

Net unrecognized tax benefit recognized

$ 16

€ 13

Income taxes, percent of tax and interest expected to be paid related to pending proceedings

33.00%

Italian Tax Audit | Other assets, net

Commitments and Contingencies

Unrecognized tax benefits

$ 6

€ 5

Italian Tax Audit | Tax Year 2013

Commitments and Contingencies

Assessed taxes including interest and penalties

$ 55

€ 48

Payment required to appeal a litigation matter or avoid collection enforcement

Italian Tax Audit | Tax Year 2014

Commitments and Contingencies

Assessed taxes including interest and penalties

$ 67

€ 58

Italian Tax Audit | Tax Year 2015

Commitments and Contingencies

Assessed taxes including interest and penalties

$ 37

€ 31

Italian Tax Audit | Tax Years 2013 And 2014

Commitments and Contingencies

Unrecognized tax benefits

$ 5

€ 4

Italian Tax Audit | Tax Years 2013 through 2019

Commitments and Contingencies

Loss Contingency, Tax, Recommended Assessment

$ 178

€ 154

Italian Tax Audit | Tax Years 2016 Through 2018

Commitments and Contingencies

Loss Contingency, Tax, Assessment

$ 132

€ 114

Turkish Tax Audit

Commitments and Contingencies

Assessed taxes including interest and penalties

₺ 801

Swiss Tax Assessment | Tax Years 2015 Through 2020

Commitments and Contingencies

Loss Contingency, Tax, Assessment

€ 50

Hawaii Tax Assessment | Tax Years 2010 Through 2020 | Subsequent Event

Commitments and Contingencies

Loss Contingency, Tax, Recommended Assessment

$ 20

Travel Transaction Related Taxes

Commitments and Contingencies

Accruals for loss contingencies

$ 59

Estimated reasonably possible loss in excess of amount accrued

Pension-related litigation

Commitments and Contingencies

Estimated reasonably possible loss in excess of amount accrued

322

278

Unfavorable Regulatory Action | Maximum

Commitments and Contingencies

Estimated possible fine per incident

$ 23

€ 20

RESTRUCTURING AND OTHER EXIT _2

RESTRUCTURING AND OTHER EXIT COSTS (Details) $ in Millions	3 Months Ended		9 Months Ended
RESTRUCTURING AND OTHER EXIT COSTS (Details) $ in Millions	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)country
Restructuring Cost and Reserve [Line Items]
Restructuring and other exit costs	$ 0	$ 41	$ 9	$ 75
Cash payments for restructuring			37
Noncash restructuring expenses and other adjustments			5
Restructuring And Related Cost Expected Cost Remaining for 2021	7		7
Restructuring And Related Cost Expected Cost Remaining for Period after 2021	4		4
Minimum
Restructuring Cost and Reserve [Line Items]
Number of countries in which the entity commenced restructuring actions \| country					60
Accrued expenses and other current liabilities
Restructuring Cost and Reserve [Line Items]
Restructuring liabilities	$ 4		$ 4		$ 37

GOVERNMENT GRANTS AND OTHER A_2

GOVERNMENT GRANTS AND OTHER ASSISTANCE (Details) - COVID-19 - USD ($) $ in Millions	3 Months Ended	4 Months Ended	9 Months Ended		15 Months Ended
	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2021
Unusual or Infrequent Item, or Both [Line Items]
Government Grant And Other Assistance Benefit (Expense)	$ 22		$ (137)	$ 122	$ 131
Grants receivable					$ 28
Government Grant and other assistance benefit that was returned, cash paid		$ 107	$ 107

OTHER INCOME (EXPENSE), NET (De

OTHER INCOME (EXPENSE), NET (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Other Income and Expenses [Abstract]
Interest and dividend income		$ 4	$ 5	$ 12	$ 49
Net (losses) gains on equity securities	[1]	(1,016)	733	(589)	1,261
Impairment of investment	[1]	0	0	0	(100)
Foreign currency transaction gains (losses)		45	(121)	92	(148)
Loss on early extinguishment of debt	[2]	0	0	(242)	0
Other	[3]	0	1	(13)	(4)
Other income (expense), net		$ (967)	$ 618	$ (740)	$ 1,058

[1]	See Note 5 for additional information related to the net (losses) gains on equity securities and impairment of investment.
[2]	See Note 9 for additional information related to the loss on early extinguishment of debt.
[3]	The amount for the nine months ended September 30, 2021 includes losses on reverse treasury lock agreements which were designated as cash flow hedges (see Note 6).

OTHER - Reconciliation of Cash

OTHER - Reconciliation of Cash and Cash Equivalents and Restricted Cash and Cash Equivalents (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 11,643	$ 10,562
Restricted cash and cash equivalents included in "Other current assets"	20	20
Total cash and cash equivalents and restricted cash and cash equivalents as shown in the Unaudited Consolidated Statements of Cash Flows	$ 11,663	$ 10,582	$ 11,217	$ 6,332

OTHER - Narrative (Details)

OTHER - Narrative (Details) € in Millions, $ in Millions	9 Months Ended
OTHER - Narrative (Details) € in Millions, $ in Millions	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021EUR (€)	Sep. 30, 2021USD ($)
Income Tax Holiday [Line Items]
Noncash investing activity related to additions to property and equipment	$ 33	$ 4
Tax and Customs Administration, Netherlands
Income Tax Holiday [Line Items]
Prepaid taxes			€ 149	$ 175