Reconciliation of Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended							3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011		Mar. 31, 2011 Trading Securities [Member]	Mar. 31, 2012 Trading Securities [Member]	Dec. 31, 2011 Trading Securities [Member]	Mar. 31, 2012 Residential Mortgage		Mar. 31, 2011 Residential Mortgage		Mar. 31, 2012 Interest Rate Contract		Mar. 31, 2011 Interest Rate Contract		Mar. 31, 2012 Equity Contract		Mar. 31, 2011 Equity Contract
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 130		$ 107		$ 6	$ 1	$ 1	$ 65		$ 46		$ 32	[1]	$ 2	[1]	$ 32	[1]	$ 53	[1]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Included In Earnings	76		11					(1)				49	[1]	24	[1]	28	[1]	(13)	[1]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Purchases Sales Issuances Settlements Maturities Paydowns Net	(8)		(18)					3		(2)		64	[1]	(16)	[1]	(75)	[1]
Sales			5		5
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Level 3 Transfers Net	6	[2]	10	[2]				6	[2]	10	[2]
Ending balance	220		105		1	1	1	67		54		17	[1]	10	[1]	135	[1]	40	[1]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Change In Unrealized Gains Losses Relating To Assets	$ 44	[3]	$ (4)	[3]				$ (1)	[3]			$ 17	[1],[3]	$ 8	[1]	$ 28	[1],[3]	$ (12)	[1]

[1] Net interest rate derivatives include derivative assets and liabilities of $21 and $4, respectively, as of March 31, 2012 and $12 and $2, respectively, as of March 31, 2011. Net equity derivatives include derivative assets and liabilities of $159 and $24, respectively, as of March 31, 2012, and $78 and $38, respectively, as of March 31, 2011.

[2] Includes residential mortgage loans held for sale that were transferred to held for investment.

[3] Includes interest income and expense.