Changes in Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	$ (53)	$ (32)	$ (79)
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	111	1	107
Accumulated Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	0	(1)	(6)
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax	(25)	(27)	(21)
Accumulated Other Comprehensive Income (Loss), Net of Tax	33	(59)	1
Cumulative Translation Adjustment, Net of Tax, Period Increase (Decrease)	0	48
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax	96	(65)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	0	(10)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, before Reclassification Adjustments, Net of Tax	(2)	(8)
Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Pension Cost, Net of Tax	4	2
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	(2)	6	11
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	94	(35)
Gain (Loss) on Derivative Used in Net Investment Hedge, after Tax	(21)	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(3)	(25)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax	14	(42)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Net of Tax	1	15
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	0	5	(6)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(21)	48	(25)
Other Comprehensive Income (Loss), Net of Tax	$ 91	$ (59)	$ (87)