Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic earnings per share: [Abstract]
Net income (loss)		$ (338)	$ 180	$ 569
Less: Undistributed earnings allocated to participating securities		0	6	16
Net income (loss) available to common stockholders		$ (338)	$ 174	$ 553
Basic weighted average shares	[1]	133,001,088	163,936,318	188,171,503
Basic		$ (2.54)	$ 1.06	$ 2.94
Diluted earnings per share: [Abstract]
Net income (loss)		$ (338)	$ 180	$ 569
Less: Undistributed earnings allocated to participating securities		0	6	15
Less: mark-to-market gain (loss) on warrants		0	0	28
Net income (loss) available to common stockholders		$ (338)	$ 174	$ 526
Basic weighted average shares	[1]	133,001,088	163,936,318	188,171,503
Stock options		0	933,470	1,104,247
Warants		0	0	1,622,877
Diluted weighted average shares		133,001,088	164,869,788	190,898,627
Diluted		$ (2.54)	$ 1.06	$ 2.76
Unvested Restricted Stock And Units That Receive Nonforfeitable Dividends Or Dividend Equivalents That Have Met Service Condition		930,406	617,909	412,769

[1] Includes 930,406, 617,909 and 412,769 of participating securities that met the service condition and were eligible to receive nonforfeitable dividends or dividend equivalents for the years ended December 31, 2016, 2015 and 2014, respectively.