Share Acitivity within Common, Preferred and Treasury Stock (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Values [Abstract]
Beginning balance	$ 14,051
Issuance of common stock	1,648		(986)
Exchange of preferred shares, Series G			269
Redemption of preferred shares, value	(3,408)
Other		(2)
Stock-based awards issued or exercised, including treasury shares issued	(8)	(4)
Ending Balance	13,201	14,051
Shares [Abstract]
Issuance of common stock			60,000,000
Stock-based awards exercised, including treasury shares issued	(96,000)	(58,000)	(11,000)
Common Stock
Values [Abstract]
Beginning balance			1,295
Issuance of common stock	272		351
Exchange of preferred shares, Series G			(133)
Shares [Abstract]
Beginning balance	801,504,188		583,427,104
Issuance of common stock	122,388,393		157,955,960
Redemption of preferred shares, Series F			60,121,124
Ending balance	923,892,581		801,504,188
Preferred Stock
Values [Abstract]
Beginning balance	(130)	(201)	4,241
Exchange of preferred shares, Series G			674
Redemption of preferred shares, value	(3,408)
Accretion from dividends on preferred shares, Series F	153	45	41
Other	(1)	(3)	(2)
Stock-based awards issued or exercised, including treasury shares issued		6	(1)
Restricted stock grants and forfeitures, net		62	27
Ending Balance		(130)	(201)
Shares [Abstract]
Beginning balance	152,771	152,771	180,620
Redemption of preferred shares, Series F	(136,320)		(27,849)
Ending balance	16,450	152,771	152,771
Treasury Stock
Values [Abstract]
Beginning balance			229
Restricted stock grants	58
Other	(1)		(2)
Stock-based awards issued or exercised, including treasury shares issued	7	(6)	1
Restricted stock grants and forfeitures, net	(58)	(62)	(27)
Employee stock ownership through benefit plans		$ (3)
Shares [Abstract]
Beginning balance	5,231,666	6,436,024	6,040,492
Other			327,200
Stock-based awards exercised, including treasury shares issued	(336,735)	16,391	819,796
Restricted stock grants and forefeitures, net	(756,381)	(1,334,967)	(751,464)
Employee stock ownership through benefit plans	(50,405)	114,218
Ending balance	4,088,145	5,231,666	6,436,024