Activity in the Allowance for Credit Losses (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011		Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Components:
Balance at beginning of period	$ 2,350		$ 2,795		$ 2,505		$ 3,032
Provision for loan losses	450		348		1,065		1,194
Provision(Benefit) for unfunded commitments	0		1		(2)		8
Loan charge-offs	(585)		(536)		(1,445)		(1,714)
Loan recoveries	74		44		162		146
Balance at end of period	2,289		2,650		2,289		2,650
ALLL	2,239		2,600		2,239		2,600		2,300	2,457	2,744	2,974
Unfunded commitments reserve	50	[1]	50	[1]	50	[1]	50	[1]
Allowance for credit losses	$ 2,289		$ 2,650		$ 2,289		$ 2,650

[1] The unfunded commitments reserve is recorded in other liabilities in the Consolidated Balance Sheets.