Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax	$ (1)	$ 1	$ 3
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	(17)	(9)	(42)
Foreign currency translation adjustments	(8)	33	(23)
Other comprehensive income before reclassifications, net of tax	(10)	31
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (18)	$ (8)	$ 39