Investment in Expedia - Intangible Assets Acquired (Details) - USD ($) $ in Millions		12 Months Ended
	Nov. 05, 2016	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, Purchase Accounting Adjustments		$ 126
Noncontrolling Interest Purchase Accounting Adjustments		167
Deferred Tax Liabilities Purchase Accounting Adjustments		$ 41
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life of intangible asset		9 years
Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life of intangible asset		5 years
Supplier Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life of intangible asset		4 years
Other | Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life of intangible asset		6 years
Other | Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life of intangible asset		1 year
Expedia
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization	$ 6,774
Useful life of intangible asset		4 years
Goodwill expected to be tax deductible	0
Expedia | Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization	$ 4,233
Useful life of intangible asset	9 years
Expedia | Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization	$ 1,480
Useful life of intangible asset	5 years
Expedia | Supplier Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization	$ 980
Useful life of intangible asset	4 years
Expedia | Other
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization	$ 81
Expedia | Other | Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life of intangible asset	6 years
Expedia | Other | Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life of intangible asset	1 year