Income Taxes - U.S. Tax Cuts and Jobs Act (Tax Act) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Net provisional income tax charge		$ 61	$ 394
U.S fedneral and state tax charge for deemed repatriation of accumulated foreign components			467
Estimated charge for foreign withholding taxes related to anticipated future repatriation of foreign earnings			260
Estimated deferred tax benefit for the revaluation of net deferred tax liabilities			(333)
Deemed repatriation tax payable	$ 291	291	422
Tax Cuts and Jobs Act, reclassification from AOCI to retained earnings, tax effect		0
Provisional Current and Deferred Tax Impact of Tax Act [Abstract]
Current tax expense (benefit)		219	414
Foreign		(36)	53
State and local		114	60
Current tax expense (benefit)		297	527
U.S. federal	6	6	(333)
State and local	7	7	0
Foreign		0	200
Deferred tax expense (benefit)		13	(133)
Tax Act income tax charge, net		310	394
Tax (benefit) charge related to the Tax Act		(61)	394
Tax related to divestitures		371
Other Noncurrent Liabilities
Income Taxes [Line Items]
Deemed repatriation tax payable	265	265	$ 388
United States
Income Taxes [Line Items]
Net provisional income tax charge		41
State and Local Jurisdiction
Income Taxes [Line Items]
Net provisional income tax charge		20
Retained Earnings
Income Taxes [Line Items]
Tax Cuts and Jobs Act, reclassification from AOCI to retained earnings, tax effect	93	$ 93
Retained Earnings | United States
Income Taxes [Line Items]
Tax Cuts and Jobs Act, reclassification from AOCI to retained earnings, tax effect	98
Retained Earnings | State and Local Jurisdiction
Income Taxes [Line Items]
Tax Cuts and Jobs Act, reclassification from AOCI to retained earnings, tax effect	$ (5)