Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Basic earnings per share: [Abstract]
Net income (loss)	$ 180	$ 569	$ 250
Less: Undistributed earnings allocated to participating securities	6	16	5
Net income (loss) available to common stockholders	$ 174	$ 553	$ 245
Basic weighted average shares	163,936,318	188,171,503	189,071,011
Basic	$ 1.06	$ 2.94	$ 1.3
Diluted earnings per share: [Abstract]
Net income (loss)	$ 180	$ 569	$ 250
Less: Undistributed earnings allocated to participating securities	6	15	5
Less: mark-to-market gain (loss) on warrants	0	28	0
Net income (loss) available to common stockholders	$ 174	$ 526	$ 245
Basic weighted average shares	163,936,318	188,171,503	189,071,011
Stock options	933,470	1,104,247	1,241,902
Warants	0	1,622,877	0
Diluted weighted average shares	164,869,788	190,898,627	190,312,913
Diluted	$ 1.06	$ 2.76	$ 1.29
Unvested Restricted Stock And Units That Receive Nonforfeitable Dividends Or Dividend Equivalents That Have Met Service Condition	617,909	412,769	629,896