Income Taxes - Narrative (Details) - USD ($)		3 Months Ended		12 Months Ended
	Feb. 18, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Examination [Line Items]
Income tax expense (benefit)		$ 658,000,000
Accumulated foreign earnings, provisional income tax expense (benefit)		676,000,000
Noncurrent income taxes payable		614,000,000	$ 0	$ 614,000,000	$ 0
Cash and equivalents		3,094,000,000	2,472,000,000	3,094,000,000	2,472,000,000	$ 3,090,000,000	$ 3,990,000,000
Additional foreign withholding tax		53,000,000
Deferred tax asset, provisional income tax expense (benefit)		82,000,000
Foreign earnings, income tax expense				75,000,000
Unrecognized tax benefits that would impact effective tax rate		254,000,000		254,000,000
Decrease in unrecognized tax benefits, settlements			96,000,000	53,000,000	96,000,000	6,000,000
Possible decrease in unrecognized tax benefits resulting from ongoing audits				31,000,000
Accrual for interest and penalties related to income tax matters		25,000,000	28,000,000	25,000,000	28,000,000
Unrecognized tax benefit		285,000,000	$ 210,000,000	285,000,000	$ 210,000,000	$ 259,000,000	$ 218,000,000
Tax Year 2006 | Internal Revenue Service (IRS)
Income Tax Examination [Line Items]
Assessment of additional taxes	$ 70,000,000
Return of Capital Under Examination
Income Tax Examination [Line Items]
Unrecognized tax benefit		0		0
Foreign Tax Authority
Income Tax Examination [Line Items]
Cash and equivalents		2,000,000,000		$ 2,000,000,000
Deferred Tax Asset Related To Performance-based Compensation
Income Tax Examination [Line Items]
Increase (decrease) in deferred income taxes		$ 11,000,000