Stockholders' Equity (Schedule of Components of Other Comprehensive Income (Loss), Net) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss), net [Line Items]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax	$ 0	$ 1	$ 0	$ 1
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax	(72)	71	(27)	99
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	6	7	10	7
Foreign currency translation	(66)	78	(17)	106
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Cash Flow Hedges Arising During Period, before Tax	6	1	4	(1)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Cash Flow Hedges Arising During Period, Tax	0	0	1	0
Gain (loss) on cash flow hedges	6	1	5	(1)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	0	0	1	5
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax	0	0	0	0
Pension and postretirement benefits	0	0	1	5
Other Comprehensive Income (Loss), before Tax	(66)	73	(22)	104
Income tax (provision) benefit	6	7	11	7
Total other comprehensive income (loss), net of tax	(60)	80	(11)	111
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	0	0	0	0
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	$ 0	$ 1	$ 0	$ 1