Stockholders' Equity (Schedule of Adjustments to Accumulated Other Comprehensive Income (Loss), Net) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance as of the beginning of the period	$ (177)	$ (358)	$ (348)
Other comprehensive income (loss) before reclassifications	(75)	174	(18)
Amounts reclassified from accumulated other comprehensive income (loss)	(1)	(5)	(4)
Income tax (provision) benefit	6	12	12
Balance as of the end of the period	(247)	(177)	(358)
Unrealized Gain (Loss) on Marketable Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance as of the beginning of the period	0	1	1
Other comprehensive income (loss) before reclassifications	0	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0
Income tax (provision) benefit	0	(1)	0
Balance as of the end of the period	0	0	1
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance as of the beginning of the period	(176)	(350)	(339)
Other comprehensive income (loss) before reclassifications	(65)	162	(22)
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0
Income tax (provision) benefit	5	12	11
Balance as of the end of the period	(236)	(176)	(350)
Gain (Loss) from Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance as of the beginning of the period	2	3	(2)
Other comprehensive income (loss) before reclassifications	(11)	4	7
Amounts reclassified from accumulated other comprehensive income (loss)	(1)	(4)	(2)
Income tax (provision) benefit	2	(1)	0
Balance as of the end of the period	(8)	2	3
Pension and Postretirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance as of the beginning of the period	(3)	(12)	(8)
Other comprehensive income (loss) before reclassifications	1	8	(3)
Amounts reclassified from accumulated other comprehensive income (loss)	0	(1)	(2)
Income tax (provision) benefit	(1)	2	1
Balance as of the end of the period	$ (3)	$ (3)	$ (12)