Pre-Tax Net Securities Gains (Losses) by Type (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	$ 40	$ (3)	$ 5
U.S. Treasury
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	38	33
FDIC-Insured Debt
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	10
Alt-A RMBS
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	(10)	(39)	5
Prime RMBS
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	(1)	(10)	9
Subprime RMBS
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	(3)	(8)	(6)
European Floating Rate Notes
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	(1)	(20)	(3)
Sovereign Debt
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	7	36
Corporate Bonds
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	2
Other Securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	$ (2)	$ 5