Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basic earnings per share: [Abstract]
Net income (loss)		$ (1,605)	$ (338)	$ 180
Less: Undistributed earnings allocated to participating securities		0	0	6
Net income (loss) available to common stockholders		$ (1,605)	$ (338)	$ 174
Basic weighted average shares	[1]	118,930,282	133,001,088	163,936,318
Basic		$ (13.5)	$ (2.54)	$ 1.06
Diluted earnings per share: [Abstract]
Net income (loss)		$ (1,605)	$ (338)	$ 180
Less: Undistributed earnings allocated to participating securities		0	0	6
Less: mark-to-market gain (loss) on warrants		0	0	0
Net income (loss) available to common stockholders		$ (1,605)	$ (338)	$ 174
Basic weighted average shares	[1]	118,930,282	133,001,088	163,936,318
Stock options		0	0	1,000,000
Diluted weighted average shares		118,930,282	133,001,088	164,869,788
Diluted		$ (13.5)	$ (2.54)	$ 1.06
Unvested Restricted Stock And Units That Receive Nonforfeitable Dividends Or Dividend Equivalents That Have Met Service Condition		311,772	930,406	617,909
Potentially dilutive securities excluded from the diluted EPS because of antidilutive effect		14,127,112	16,506,438	17,967,871

[1] Includes 0.3 million, 0.9 million and 0.6 million of participating securities that met the service condition and were eligible to receive nonforfeitable dividends or dividend equivalents for the years ended December 31, 2017, 2016 and 2015, respectively.