Incomes Taxes (Income tax (benefit) provision) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
United States, current federal tax expense (benefit)	$ 138	$ 34	$ 98
Current foreign tax expense (benefit)	213	167	181
Current state and local tax expense (benefit)	12	7	10
Current income tax expense (benefit)	363	208	289
United States, deferred federal income tax expense (benefit)	386	120	55
Deferred foreign income tax expense (benefit)	(233)	(154)	(143)
Deferred state and local income tax expense (benefit)	34	12	8
Deferred income tax expense (benefit)	187	(22)	(80)
Total income tax expense	$ 550	$ 186	$ 209