Income Taxes - Narrative (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
	Feb. 18, 2014	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Examination [Line Items]
Income tax expense (benefit)			$ 658		$ 658
Accumulated foreign earnings, provisional income tax expense (benefit)			676
Noncurrent income taxes payable			614	$ 495	$ 614
Additional foreign withholding tax			53
Deferred tax asset, provisional income tax expense (benefit)			(82)
Effective tax rate				24.50%	48.40%	30.00%
Effective income tax rate reconciliation, change in deferred tax assets valuation allowance		$ 37
Effective tax rate, share-based compensation, excess tax benefit, amount				$ 10	$ 50
Effective tax rate, tax credit, foreign		$ 22
Accrual foreign withhold taxes			75	71	75
Unrecognized tax benefits that would impact effective tax rate				268
Decrease in unrecognized tax benefits, settlements				5	53	$ 96
Possible decrease in unrecognized tax benefits resulting from ongoing audits				42
Accrual for interest and penalties related to income tax matters			25	25	$ 25
Undistributed earnings of foreign subsidiaries				$ 6,000
Tax Year 2006 | Internal Revenue Service (IRS)
Income Tax Examination [Line Items]
Assessment of additional taxes	$ 70
Deferred Tax Asset Related To Performance-based Compensation
Income Tax Examination [Line Items]
Increase (decrease) in deferred income taxes			$ (11)