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, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Basic earnings per share: [Abstract]
Net income (loss)	$ 64	$ 120	$ 133	$ 376
Less: Undistributed earnings allocated to participating securities	2	4	4	10
Net income (loss) available to common stockholders	$ 62	$ 116	$ 129	$ 366
Basic weighted average shares	172,146,651	189,169,042	176,914,777	189,101,884
Net income (loss) per basic common share	$ 0.36	$ 0.61	$ 0.73	$ 1.93
Diluted earnings per share: [Abstract]
Net income (loss)	$ 64	$ 120	$ 133	$ 376
Less: Undistributed earnings allocated to participating securities	2	3	4	9
Less: mark-to-market gain (loss) on warrants	0	30	0	14
Net income (loss) available to common stockholders	$ 62	$ 87	$ 129	$ 353
Basic weighted average shares	172,146,651	189,169,042	176,914,777	189,101,884
Stock options	1,007,668	1,111,816	1,004,181	1,170,182
Warants	0	2,626,013	0	2,779,370
Diluted weighted average shares	173,154,319	192,906,871	177,918,958	193,051,436
Net income (loss) per diluted common share	$ 0.36	$ 0.45	$ 0.72	$ 1.83
Unvested Restricted Stock And Units That Receive Nonforfeitable Dividends Or Dividend Equivalents That Have Met Service Condition	581,102	270,443	629,569	337,827