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, 2013		Mar. 31, 2012		Mar. 31, 2013 Trading Securities	Dec. 31, 2012 Trading Securities	Mar. 31, 2012 Trading Securities	Dec. 31, 2011 Trading Securities	Mar. 31, 2013 Residential Mortgage		Mar. 31, 2012 Residential Mortgage		Mar. 31, 2013 Interest Rate Contract		Mar. 31, 2012 Interest Rate Contract		Mar. 31, 2013 Equity Contract		Mar. 31, 2012 Equity Contract
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	$ 278		$ 130		$ 1	$ 1	$ 1	$ 1	$ 76		$ 65		$ 57	[1]	$ 32	[1]	$ 144	[1]	$ 32	[1]
Total gains or losses (realized/unrealized):
Included in earnings	84		76						1		(1)		56	[1]	49	[1]	27	[1]	28	[1]
Settlements	66		(8)						4		3		65	[1]	64	[1]	(3)	[1]	(75)	[1]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Level 3 Transfers Net	8	[2]	6	[2]					8	[2]	6	[2]
Ending balance	304		220		1	1	1	1	81		67		48	[1]	17	[1]	174	[1]	135	[1]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Change In Unrealized Gains Losses Relating To Assets	$ 79	[3]	$ 44	[3]					$ 1	[3]	$ (1)	[3]	$ 51	[1],[3]	$ 17	[1],[3]	$ 27	[1],[3]	$ 28	[3]

[1] Net interest rate derivatives include derivative assets and liabilities of $51 and $3, respectively, as of March 31, 2013 and $21 and $4, respectively, as of March 31, 2012. Net equity derivatives include derivative assets and liabilities of $211 and $37, respectively, as of March 31, 2013, and $159 and $24, respectively, as of March 31, 2012.

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

[3] Includes interest income and expense.