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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Basic earnings per share: [Abstract]
Net income (loss)	$ 31	$ (35)	$ (73)	$ 98
Less: Undistributed earnings allocated to participating securities	1	0	0	3
Net income (loss) available to common stockholders	$ 30	$ (35)	$ (73)	$ 95
Basic weighted average shares	131,633,411	155,239,723	133,368,752	169,610,370
Basic	$ 0.23	$ (0.23)	$ (0.55)	$ 0.56
Diluted earnings per share: [Abstract]
Net income (loss)	$ 31	$ (35)	$ (73)	$ 98
Less: Undistributed earnings allocated to participating securities	1	0	0	3
Less: mark-to-market gain (loss) on warrants			0	0
Net income (loss) available to common stockholders	$ 30	$ (35)	$ (73)	$ 95
Basic weighted average shares	131,633,411	155,239,723	133,368,752	169,610,370
Stock options	408,656	0	0	956,016
Warants			0	0
Diluted weighted average shares	132,042,067	155,239,723	133,368,752	170,566,386
Diluted	$ 0.23	$ (0.23)	$ (0.55)	$ 0.55
Unvested Restricted Stock And Units That Receive Nonforfeitable Dividends Or Dividend Equivalents That Have Met Service Condition	955,217	600,826	867,160	619,889