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	9 Months Ended				3 Months Ended												9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013 Quarter to date		Sep. 30, 2012 Quarter to date		Sep. 30, 2013 Trading Securities	Dec. 31, 2012 Trading Securities	Sep. 30, 2012 Trading Securities	Dec. 31, 2011 Trading Securities	Sep. 30, 2013 Trading Securities Quarter to date	Jun. 30, 2013 Trading Securities Quarter to date	Sep. 30, 2012 Trading Securities Quarter to date	Jun. 30, 2012 Trading Securities Quarter to date	Sep. 30, 2013 Residential Mortgage		Sep. 30, 2012 Residential Mortgage		Sep. 30, 2013 Residential Mortgage Quarter to date		Sep. 30, 2012 Residential Mortgage Quarter to date		Sep. 30, 2013 Interest Rate Contract		Sep. 30, 2012 Interest Rate Contract		Sep. 30, 2013 Interest Rate Contract Quarter to date		Sep. 30, 2012 Interest Rate Contract Quarter to date		Sep. 30, 2013 Equity Contract		Sep. 30, 2012 Equity Contract		Sep. 30, 2013 Equity Contract Quarter to date		Sep. 30, 2012 Equity Contract Quarter to date
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance	$ 278		$ 130		$ 304		$ 315		$ 1	$ 1	$ 1	$ 1	$ 1	$ 1	$ 1	$ 1	$ 76		$ 65		$ 83		$ 76		$ 57	[1]	$ 32	[1]	$ (30)	[1]	$ 54	[1]	$ 144	[1]	$ 32	[1]	$ 250	[1]	$ 184	[1]
Included in earnings	143		395		48		147										(1)						1		42	[1]	338	[1]	43	[1]	163	[1]	102	[1]	57	[1]	5	[1]	(17)	[1]
Purchases	(1)				(1)																				(1)	[1]			(1)	[1]
Settlements	(77)		(194)		7		(114)										(12)		(10)		(5)		(5)		(77)	[1]	(271)	[1]	9	[1]	(118)	[1]	12	[1]	87	[1]	3	[1]	9	[1]
Transfers Into Level 3	26	[2]	21	[2]	11	[2]	4	[2]									26	[2]	21	[2]	11	[2]	4	[2]
Ending Balance	369		352		369		352		1	1	1	1	1	1	1	1	89		76		89		76		21	[1]	99	[1]	21	[1]	99	[1]	258	[1]	176	[1]	258	[1]	176	[1]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Change In Unrealized Gains Losses Relating To Assets	$ 146	[3]	$ 230	[3]	$ 27	[3]	$ 85	[3]									$ (1)	[3]					$ 1	[3]	$ 45	[1],[3]	$ 173	[1],[3]	$ 22	[1],[3]	$ 101	[1],[3]	$ 102	[1],[3]	$ 57	[1],[3]	$ 5	[1],[3]	$ (17)	[1],[3]

[1] Net interest rate derivatives include derivative assets and liabilities of $25 and $4, respectively, as of September 30, 2013 and $102 and $3, respectively, as of September 30, 2012. Net equity derivatives include derivative assets and liabilities of $293 and $35, respectively, as of September 30, 2013, and $198 and $22, respectively, as of September 30, 2012.

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

[3] Includes interest income and expense.