Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic earnings per share: [Abstract]
Net income (loss)	$ (1,229)	$ (27)	$ (1,301)	$ (105)
Less: Undistributed earnings allocated to participating securities	0	0	0	0
Net income (loss) available to common stockholders	$ (1,229)	$ (27)	$ (1,301)	$ (105)
Basic weighted average shares	125,653,189	132,677,066	128,511,897	134,245,952
Basic	$ (9.78)	$ (0.2)	$ (10.13)	$ (0.78)
Diluted earnings per share: [Abstract]
Net income (loss)	$ (1,229)	$ (27)	$ (1,301)	$ (105)
Less: Undistributed earnings allocated to participating securities	0	0	0	0
Less: mark-to-market gain (loss) on warrants			0	0
Net income (loss) available to common stockholders	$ (1,229)	$ (27)	$ (1,301)	$ (105)
Basic weighted average shares	125,653,189	132,677,066	128,511,897	134,245,952
Stock options	0	0	0	0
Warants			0	0
Diluted weighted average shares	125,653,189	132,677,066	128,511,897	134,245,952
Diluted	$ (9.78)	$ (0.2)	$ (10.13)	$ (0.78)
Unvested Restricted Stock And Units That Receive Nonforfeitable Dividends Or Dividend Equivalents That Have Met Service Condition	300,000	900,000	300,000	800,000