Reconciliation of Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015		Sep. 30, 2014
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance						$ 484		$ 437
Included in earnings						280		52
Purchases						(1)
Settlements						(88)		(91)
Transfers Into Level 3	[1]					86		24
Ending Balance		$ 761		$ 422		761		422
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	[2]					210		(32)
Quarter to date
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance		633		473
Included in earnings		161		(38)
Settlements		(35)		(25)
Transfers Into Level 3	[1]	2		12
Ending Balance		761		422		761		422
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	[2]	142		(46)
Trading Securities
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance								1
Ending Balance				1				1
Trading Securities | Quarter to date
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance				1
Ending Balance				1				1
Residential Mortgage
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance						108		92
Included in earnings						2		3
Settlements						(23)		(10)
Transfers Into Level 3	[1]					86		24
Ending Balance		173		109		173		109
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	[2]					2		3
Residential Mortgage | Quarter to date
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance		178		99
Included in earnings		1		1
Settlements		(8)		(3)
Transfers Into Level 3	[1]	2		12
Ending Balance		173		109		173		109
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	[2]	1		1
Interest Rate Contract
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance						10	[3]	8	[4]
Included in earnings						90	[3]	94	[4]
Purchases	[3]					(1)
Settlements						(83)	[3]	(95)	[4]
Ending Balance		16	[3]	7	[4]	16	[3]	7	[4]
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	[2]					20	[3]	10	[4]
Interest Rate Contract | Quarter to date
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance		10	[3]	15	[4]
Included in earnings		38	[3]	18	[4]
Settlements		(32)	[3]	(26)	[4]
Ending Balance		16	[3]	7	[4]	16	[3]	7	[4]
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	[2]	19	[3]	10	[4]
Equity Contract
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance						366	[3]	336	[4]
Included in earnings						188	[3]	(45)	[4]
Settlements						18	[3]	14	[4]
Ending Balance		572	[3]	305	[4]	572	[3]	305	[4]
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	[2]					188	[3]	(45)	[4]
Equity Contract | Quarter to date
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance		445	[3]	358	[4]
Included in earnings		122	[3]	(57)	[4]
Settlements		5	[3]	4	[4]
Ending Balance		572	[3]	305	[4]	$ 572	[3]	$ 305	[4]
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	[2]	$ 122	[3]	$ (57)	[4]

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

[2] Includes interest income and expense.

[3] Net interest rate derivatives include derivative assets and liabilities of $19 and $3, respectively, as of September 30, 2015. Net equity derivatives include derivative assets and liabilities of $630 and $58, respectively, as of September 30, 2015.

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