Stockholders' Equity (Schedule of Components of Other Comprehensive Income (Loss), Net) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stockholders' Equity Note [Abstract]
Unrealized gain (loss) on marketable securities, gross amount	$ 0	$ 0	$ 0	$ 1
Unrealized gain (loss) on marketable securities, income tax (provision) benefit	0	0	0	0
Unrealized gain (loss) on marketable securities, net	0	0	0	1
Foreign currency translation gain (loss), gross amount	(31)	44	(58)	143
Foreign currency translation gain (loss), income tax (provision) benefit	(4)	(2)	6	5
Foreign currency translation gain (loss), net	(35)	42	(52)	148
Gain (loss) on cash flow hedges, gross amount	4	0	8	(1)
Gain (loss) on cash flow hedges, income tax (provision) benefit	0	0	1	0
Gain (loss) on cash flow hedges, net	4	0	9	(1)
Pension and postretirement benefits gain (loss), gross amount	0	(1)	1	4
Pension and postretirement benefits gain (loss), income tax (provision) benefit	0	0	0	0
Pension and postretirement benefits gain (loss), net	0	(1)	1	4
Other Comprehensive Income (Loss), before Tax	(27)	43	(49)	147
Income tax (provision) benefit	(4)	(2)	7	5
Total other comprehensive income (loss), net of tax	$ (31)	$ 41	$ (42)	$ 152