Stockholders' Equity (Schedule of Components of Other Comprehensive Income (Loss), Net) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Comprehensive Income (Loss) [Line Items]
Unrealized gain (loss) on marketable securities, gross amount	$ 0	$ 0	$ 0
Unrealized gain (loss) on marketable securities, income tax (provision) benefit	0	(1)	0
Unrealized gain (loss) on marketable securities, net amount	0	(1)	0
Foreign currency translation, gross amount	(65)	162	(22)
Foreign currency translation, income tax (provision) benefit	5	12	11
Foreign currency translation, net amount	(60)	174	(11)
Gain (loss) on cash flow hedges, gross amount	(12)	0	5
Gain (loss) on cash flow hedges, income tax (provision) benefit	2	(1)	0
Gain (loss) on cash flow hedges, net amount	(10)	(1)	5
Pension and postretirement benefits, gross amount	1	7	(5)
Pension and postretirement benefits, income tax (provision) benefit	(1)	2	1
Pension and postretirement benefits, net amount	0	9	(4)
Total other comprehensive income (loss), gross amount	(76)	169	(22)
Total other comprehensive income (loss), income tax (provision) benefit	6	12	12
Total other comprehensive income (loss), net of tax	$ (70)	$ 181	$ (10)