Net Income Per Share (Reconciliation Of Earnings Attributable To Common Stockholders, Basic And Diluted) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement Operating Activities Segment [Line Items]
Income (loss) from continuing operations attributable to parent	$ 233	$ (268)	$ 191	$ (535)
Participating Securities, Distributed and Undistributed Earnings, Basic	(2)	0	(2)	0
Basic income (loss) from continuing operations attributable to common stockholders	231	(268)	189	(535)
Diluted income (loss) from continuing operations attributable to common stockholders	$ 231	$ (268)	$ 189	$ (538)