Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax	$ 1	$ 3	$ 4
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	(2)	(1)
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	(9)	(42)	(19)
Foreign currency translation adjustments	33	(23)	(88)
Other comprehensive income before reclassifications, net of tax	31	(24)
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (8)	$ (39)	$ (15)