Reconciliation of Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail) (Quarter to date, USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2013
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance	$ 484		$ 437
Included in earnings	90		3
Settlements	(29)		(30)
Transfers Into Level 3	23	[1]	12	[1]
Ending Balance	568		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	74	[2]	(18)	[2]
Trading Securities
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance					1
Ending Balance			1		1
Residential Mortgage
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance	108		92
Included in earnings	2		1
Settlements	(7)		(2)
Transfers Into Level 3	23	[1]	12	[1]
Ending Balance	126		103
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]	1	[2]
Interest Rate Contract
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance	10	[3]	8	[3]
Included in earnings	35	[3]	37	[3]
Settlements	(28)	[3]	(32)	[3]
Ending Balance	17	[3]	13	[3]
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	19	[2],[3]	16	[2],[3]
Equity Contract
FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollforward
Beginning Balance	366	[3]	336	[3]
Included in earnings	53	[3]	(35)	[3]
Settlements	6	[3]	4	[3]
Ending Balance	425	[3]	305	[3]
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	$ 53	[2],[3]	$ (35)	[2],[3]

[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 $2, respectively, as of March 31, 2015 and $16 and $3, respectively, as of March 31, 2014. Net equity derivatives include derivative assets and liabilities of $485 and $60, respectively, as of March 31, 2015, and $348 and $43, respectively, as of March 31, 2014.