Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended						9 Months Ended
	Sep. 30, 2014		Jun. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013		Jun. 30, 2013		Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Trading assets	$ 22,099						$ 22,099				$ 28,894
Trading liabilities	9,177						9,177				10,875
Fair value of assets	3,515		3,581		2,575		3,515		2,575		3,150		2,615		3,690
Loss severity, trust preferred securities							1.8
Fair Value Assets, Transfers Out of Level 3	1				4		101		25
Fair Value Liability, Transfers Out of Level 3	476				103		772		527
Fair Value Liability, Transfers Into Level 3	(61)				(109)		(110)		(266)
Average deviation of implied volatility, foreign currency pair							4.00%
Average deviation of implied volatility, at-the-money equity option							5.00%
Revaluation period							45 days
Weighted Average [Member] | Residential Mortgage [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value Inputs, Loss Severity							70.00%
Weighted Average [Member] | Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value Inputs, Loss Severity							25.00%
Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets	466				897		466		897
Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets	231				618		231		618
Credit contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets	221		257	[1]	213	[1]	221		213	[1]	191	[1]	225	[1]	571	[1]
Fair Value Assets, Transfers Out of Level 3	0	[1]			0	[1]	(114)	[1]	0	[1]
Government debt securities issued by foreign entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets	0		0		121		0		121		121		135		311
Fair Value Assets, Transfers Out of Level 3	0		119		0		119		0
Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Trading assets	4,646						4,646				5,991
Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Trading liabilities	5,552						5,552				6,741
Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value Liability, Transfers Out of Level 3	395				79		591		323
Fair Value Liability, Transfers Into Level 3	(59)				(84)		(108)		(241)
Other liabilities [Member] | Standby Letters of Credit [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Deferred fees on standby letters of credit	$ 41						$ 41				$ 46

[1] Level 3 net derivatives included derivative assets of $466 million and derivative liabilities of $231 million as of September 30, 2014 and derivative assets of $897 million and derivative liabilities of $618 million as of September 30, 2013.