Allowance for Credit Losses Activity (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	$ 43,028	$ 43,979
Overdrafts
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	3,715	4,849
Domestic
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	33,747	33,971
Domestic | Overdrafts
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	1,971	2,958	3,381
Domestic | Margin Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	13,144	12,760	9,369
Domestic | Other loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	$ 849	$ 623	$ 452