Share Acitivity within Common, Preferred and Treasury Stock (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended						12 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Common Stock	Dec. 31, 2012 Common Stock	Dec. 31, 2009 Common Stock	Dec. 31, 2011 Preferred Stock	Dec. 31, 2010 Preferred Stock	Dec. 31, 2012 Preferred Stock	Dec. 31, 2012 Treasury Stock	Dec. 31, 2011 Treasury Stock	Dec. 31, 2010 Treasury Stock
Values [Abstract]
Beginning balance	$ 13,201			$ 1,779	$ 2,051	$ 1,779	$ 3,654	$ 3,609	$ 398	$ 64	$ 130	$ 201
Issuance of common stock		1,648		272
Redemption of preferred shares, value		(3,408)					(3,408)
Accretion from dividends on preferred shares, Series F							153	45
Restricted stock grants										47	58	62
Shares acquired for treasury	(650)									(627)
Other							(1)			(3)	(1)	(3)
Stock-based awards issued or exercised, including treasury shares issued	(20)	(8)	4							7	7	6
Ending Balance	$ 13,716	$ 13,201		$ 2,051	$ 2,051	$ 1,779	$ 398	$ 3,654	$ 398	$ 634	$ 64	$ 130
Shares [Abstract]
Beginning balance				801,504,188	923,892,581	801,504,188	152,771	152,771	16,450	4,088,145	5,231,666	6,436,024
Issuance of common stock				122,388,393
Exchange of preferred shares, Series G							(1)
Redemption of preferred shares, Series F							(136,320)
Treasury Stock Shares Acquired Cost Method										42,424,014
Other											(50,405)	114,218
Stock-based awards exercised, including treasury shares issued	(205,000)	(96,000)	(58,000)							(1,776,508)	(336,735)	16,391
Restricted stock grants and forefeitures, net										(2,877,657)	(756,381)	(1,334,967)
Employee stock ownership through benefit plans										(117,470)
Ending balance				923,892,581	923,892,581	801,504,188	16,450	152,771	16,450	41,740,524	4,088,145	5,231,666