Net Income Per Share (Reconciliation Of Earnings Attributable To Common Stockholders, Basic And Diluted) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement Operating Activities Segment [Line Items]
Basic income (loss) from continuing operations attributable to common stockholders	$ 22	$ 640	$ (513)	$ 347
Diluted income (loss) from continuing operations attributable to common stockholders	22	640	(513)	347
Continuing Operations [Member]
Statement Operating Activities Segment [Line Items]
Income (loss) from continuing operations attributable to parent	22	648	(513)	356
Participating Securities, Distributed and Undistributed Earnings, Basic	0	(6)	0	(3)
Basic income (loss) from continuing operations attributable to common stockholders	22	642	(513)	353
Diluted income (loss) from continuing operations attributable to common stockholders	22	642	(513)	353
Discontinued Operations [Member]
Statement Operating Activities Segment [Line Items]
Basic income (loss) from continuing operations attributable to common stockholders	0	(2)	0	(6)
Diluted income (loss) from continuing operations attributable to common stockholders	$ 0	$ (2)	$ 0	$ (6)