Allowance for Credit Losses Activity (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Jun. 30, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	$ 45,431		$ 43,979
Domestic
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	35,249		33,971
Overdrafts
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	5,655		4,849
Overdrafts | Domestic
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	2,750	1,971	2,958	4,629
Margin Loans | Domestic
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	13,462	13,144	12,760	9,520
Other loans | Domestic
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	$ 599	$ 849	$ 623	$ 597