Derivative Positions (Parenthetical) (Detail) (Nondesignated, USD $) Share data in Millions, unless otherwise specified									1 Months Ended
	Mar. 31, 2013 Trading Activity	Dec. 31, 2012 Trading Activity	Mar. 31, 2013 Derivative Financial Instruments, Assets Trading Activity	Dec. 31, 2012 Derivative Financial Instruments, Assets Trading Activity	Mar. 31, 2013 Derivative Financial Instruments, Liabilities [Member]	Dec. 31, 2012 Derivative Financial Instruments, Liabilities [Member]	Mar. 31, 2013 Derivative Financial Instruments, Liabilities [Member] Future	Dec. 31, 2012 Derivative Financial Instruments, Liabilities [Member] Future	May 31, 2009 Derivative Financial Instruments, Liabilities [Member] Visa Interest
Notional amounts related to interest rate futures			$ 19,400,000,000	$ 16,200,000,000			$ 1,300,000,000	$ 1,700,000,000
Notional related to equity futures			1,800,000,000	800,000,000
Asset amount notional from purchased and written interest rate swap risk participation agreements	3,000,000	3,000,000
Number Of Shares Sold To Selected Financial Institutions									3.2
Notional Amount Derivative Liability Sale Of Shares					134,000,000	134,000,000
Notional Amount Liability Purchased And Written Interest Rate Swap Risk Participation Agreements	$ 4,000,000	$ 3,000,000