Stockholders' Equity (Schedule of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		$ 3,106	$ 3,284	$ 3,117	$ 3,350
Translation adjustment	[1]	2	(2)	2	(3)
Ending balance		3,038	3,244	3,038	3,244
Translation adjustment, net of tax expense (benefit)		1	(1)	1	(1)
Total Stockholders’ Accumulated Other Comprehensive Loss, net of taxes
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(30)	(31)	(30)	(30)
Ending balance		(28)	(33)	(28)	(33)
Post-Retirement Benefit Plans, net of taxes
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance				(16)	(20)
Translation adjustment				0	0
Ending balance		(16)	(20)	(16)	(20)
Translation Adjustment, net of taxes(1)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance				(14)	(10)
Translation adjustment				2	(3)
Ending balance		$ (12)	$ (13)	$ (12)	$ (13)

[1] Translation adjustment is presented net of tax expense of $1 million for the quarter and six months ended June 30, 2019. For the quarter and six months ended June 30, 2018, translation adjustment is presented net of tax benefit of $1 million.