Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Basic earnings per share: [Abstract]
Net income (loss)	$ 69	$ 256
Less: Undistributed earnings allocated to participating securities	2	5
Net income (loss) available to common stockholders	67	251
Basic weighted average shares	181,735,876	189,033,982
Net income (loss) per basic common share	$ 0.37	$ 1.33
Diluted earnings per share: [Abstract]
Net income (loss)	69	256
Less: Undistributed earnings allocated to participating securities	2	5
Net income (loss) available to common stockholders	$ 67	$ 251
Basic weighted average shares	181,735,876	189,033,982
Stock options	1,000,539	1,229,766
Warants	0	0
Diluted weighted average shares	182,736,415	190,263,748
Net income (loss) per diluted common share	$ 0.37	$ 1.32
Unvested Restricted Stock And Units That Receive Nonforfeitable Dividends Or Dividend Equivalents That Have Met Service Condition	678,568	405,961