Reconciliation of Net Income/(Loss) to Net Income/(Loss) Available to Common Shareholders (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net income	$ 1,958	$ 647	$ 189
Dividends, Preferred Stock, Cash	(12)	(7)	(7)
Dividends and accretion of discount on preferred stock issued to the U.S. Treasury	0	(66)	(267)
Preferred Stock, Accretion of Redemption Discount		0	0
Undistributed Earnings Allocated to Participating Securities	15	5	2
Net income/(loss) available to common shareholders	1,931	495	(87)
Average basic common shares	534,149,000	523,995,000	495,361,000
Stock options	1,000,000	2,000,000	1,000,000
Restricted stock	3,000,000	2,000,000	3,000,000
Average diluted common shares	538,061,000	527,618,000	498,744,000
Net income/(loss) per average common share - diluted	$ 3.59	$ 0.94	$ (0.18)
Net income/(loss) per average common share - basic	$ 3.62	$ 0.94	$ (0.18)
Series C and Series D Preferred Stock [Member]
Preferred Stock, Accretion of Redemption Discount		74
Stock Redeemed or Called During Period, Value		4,850
Retained Earnings [Member]
Net income	1,958	647	189
Dividends, Preferred Stock, Cash	(12)	(7)	(7)
Retained Earnings [Member] | Series C and Series D Preferred Stock [Member]
Preferred Stock, Accretion of Redemption Discount		6	25
Stock Redeemed or Called During Period, Value	$ 0	$ 74	$ 0