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, 2014		Sep. 30, 2013		Sep. 30, 2014 Quarter to date		Sep. 30, 2013 Quarter to date		Sep. 30, 2014 Trading Securities	Dec. 31, 2013 Trading Securities	Sep. 30, 2013 Trading Securities	Dec. 31, 2012 Trading Securities	Sep. 30, 2014 Trading Securities Quarter to date	Jun. 30, 2014 Trading Securities Quarter to date	Sep. 30, 2013 Trading Securities Quarter to date	Jun. 30, 2013 Trading Securities Quarter to date	Sep. 30, 2014 Residential Mortgage		Sep. 30, 2013 Residential Mortgage		Sep. 30, 2014 Residential Mortgage Quarter to date		Sep. 30, 2013 Residential Mortgage Quarter to date		Sep. 30, 2014 Interest Rate Contract		Sep. 30, 2013 Interest Rate Contract		Sep. 30, 2014 Interest Rate Contract Quarter to date		Sep. 30, 2013 Interest Rate Contract Quarter to date		Sep. 30, 2014 Equity Contract		Sep. 30, 2013 Equity Contract		Sep. 30, 2014 Equity Contract Quarter to date		Sep. 30, 2013 Equity Contract Quarter to date
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance	$ 437		$ 278		$ 473		$ 304		$ 1	$ 1	$ 1	$ 1	$ 1	$ 1	$ 1	$ 1	$ 92		$ 76		$ 99		$ 83		$ 8	[1]	$ 57	[1]	$ 15	[1]	$ (30)	[1]	$ 336	[1]	$ 144	[1]	$ 358	[1]	$ 250	[1]
Included in earnings	52		143		(38)		48										3		(1)		1				94	[1]	42	[1]	18	[1]	43	[1]	(45)	[1]	102	[1]	(57)	[1]	5	[1]
Purchases			(1)				(1)																				(1)	[1]			(1)	[1]
Settlements	(91)		(77)		(25)		7										(10)		(12)		(3)		(5)		(95)	[1]	(77)	[1]	(26)	[1]	9	[1]	14	[1]	12	[1]	4	[1]	3	[1]
Transfers Into Level 3	24	[2]	26	[2]	12	[2]	11	[2]									24	[2]	26	[2]	12	[2]	11	[2]
Ending Balance	422		369		422		369		1	1	1	1	1	1	1	1	109		89		109		89		7	[1]	21	[1]	7	[1]	21	[1]	305	[1]	258	[1]	305	[1]	258	[1]
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	$ (32)	[3]	$ 146	[3]	$ (46)	[3]	$ 27	[3]									$ 3	[3]	$ (1)	[3]	$ 1	[3]			$ 10	[1],[3]	$ 45	[1],[3]	$ 10	[1],[3]	$ 22	[1],[3]	$ (45)	[1],[3]	$ 102	[1],[3]	$ (57)	[1],[3]	$ 5	[1],[3]

[1] Net interest rate derivatives include derivative assets and liabilities of $10 and $3, respectively, as of September 30, 2014 and $25 and $4, respectively, as of September 30, 2013. Net equity derivatives include derivative assets and liabilities of $358 and $53, respectively, as of September 30, 2014, and $293 and $35, respectively, as of September 30, 2013.

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

[3] Includes interest income and expense.