Pre-Tax Net Securities Gains (Losses) by Type (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	$ 50	$ 40	$ 48	$ 90	$ 53
U.S. Treasury
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	44	38	41	82	41
Sovereign Debt
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	61	7		68
FDIC-Insured Debt
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)		10		10
Corporate Bonds
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	7	2		9
Prime RMBS
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	(1)	(1)		(2)	9
Alt-A RMBS
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	(3)	(10)	(1)	(13)	4
Trust Preferred Securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	(18)			(18)
European Floating Rate Notes
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	(22)	(1)	(12)	(23)	(15)
Subprime RMBS
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	(23)	(3)	(6)	(26)	(12)
Agency RMBS
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)			8		8
Other Securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net securities gains (losses)	$ 5	$ (2)	$ 18	$ 3	$ 18