Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss) (AOCI) - Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	$ (242)	$ (199)
Tax Cuts and Jobs Act Reclassification from AOCI to Retained Earnings Tax Effect	1
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(41)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	3
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(44)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(224)	(183)
Tax Cuts and Jobs Act Reclassification from AOCI to Retained Earnings Tax Effect	0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(41)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(41)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(19)	(15)
Tax Cuts and Jobs Act Reclassification from AOCI to Retained Earnings Tax Effect	1
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	5
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(5)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	1	$ (1)
Tax Cuts and Jobs Act Reclassification from AOCI to Retained Earnings Tax Effect	0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(2)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ 2