Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss) (AOCI) - Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	$ (224)	$ (199)
Tax Cuts and Jobs Act Reclassification from AOCI to Retained Earnings Tax Effect	1
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(23)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	3
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(26)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(210)	(183)
Tax Cuts and Jobs Act Reclassification from AOCI to Retained Earnings Tax Effect	0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(27)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(27)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(17)	(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	3
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(3)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	3	$ (1)
Tax Cuts and Jobs Act Reclassification from AOCI to Retained Earnings Tax Effect	0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	4
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ 4