Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended			12 Months Ended
	Oct. 01, 2016	Dec. 31, 2018	Jun. 30, 2018	Sep. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (Loss) on Investments					$ (111)	$ (14)	$ (12)
Net gains(losses) from foreign currency forward contracts					47	17	(66)
Impairment of goodwill					86	0	0
Investments without readily determinable fair values		$ 476			476	371
Foreign currency forward contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional amount of foreign currency derivatives		2,800			2,800
Recurring Basis | Foreign currency forward contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency forward contracts, Assets		22			22	6
Nonrecurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finite-lived intangible assets, fair value disclosure		27			27
Loss on sale of cost method Investments						9
Investments without readily determinable fair values							1
Equity securities, gain (loss)					33	(14)
Equity securities, other-than-temporary impairments						6	12
Nonrecurring Basis | Trade Names
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of indefinite-lived intangible assets	$ 33			$ 2			35
Fair value of indefinite-lived intangible assets							$ 76
Despegar.com Corp.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (Loss) on Investments					(145)
Despegar.com Corp. | Available-for-sale Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost						273
Accumulated gross unrealized loss						$ 9
Reporting Unit Within Core Online Travel Companies [Member] | Nonrecurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of goodwill		$ 25	$ 61		86
Impairment of indefinite-lived intangible assets					$ 42