Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic earnings per share: [Abstract]
Net income (loss)	$ (267)	$ 31	$ (1,568)	$ (73)
Less: Undistributed earnings allocated to participating securities	0	1	0	0
Net income (loss) available to common stockholders	$ (267)	$ 30	$ (1,568)	$ (73)
Basic weighted average shares	122,967,924	131,633,411	126,643,642	133,368,752
Basic	$ (2.17)	$ 0.23	$ (12.38)	$ (0.55)
Diluted earnings per share: [Abstract]
Net income (loss)	$ (267)	$ 31	$ (1,568)	$ (73)
Less: Undistributed earnings allocated to participating securities	0	1	0	0
Less: mark-to-market gain (loss) on warrants			0	0
Net income (loss) available to common stockholders	$ (267)	$ 30	$ (1,568)	$ (73)
Basic weighted average shares	122,967,924	131,633,411	126,643,642	133,368,752
Stock options	0	408,656	0	0
Warants			0	0
Diluted weighted average shares	122,967,924	132,042,067	126,643,642	133,368,752
Diluted	$ (2.17)	$ 0.23	$ (12.38)	$ (0.55)
Unvested Restricted Stock And Units That Receive Nonforfeitable Dividends Or Dividend Equivalents That Have Met Service Condition	300,000	900,000	300,000	900,000