Activity in the Allowance for Credit Losses (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011		Dec. 31, 2011	Dec. 31, 2010
Components:
Balance at beginning of period	$ 2,505		$ 3,032
Provision for loan losses	313		451
Provision(Benefit) for unfunded commitments	4		(4)
Loan charge-offs	(463)		(615)
Loan recoveries	41		44
Balance at end of period	2,400		2,908
ALLL	2,348		2,854		2,457	2,974
Unfunded commitments reserve	52	[1]	54	[1]
Allowance for credit losses	$ 2,400		$ 2,908

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