Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Jun. 30, 2013		Dec. 31, 2012		Jun. 30, 2012		Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	$ 25,527				$ 25,527						$ 30,874
Trading liabilities	11,065				11,065						14,699
Fair value assets	2,575		3,555		2,575		3,555		2,615		3,690		4,006		4,157
Loss severity rate					1.8
Foreign currecy implied volatility					4.40%
Equity implied volatility					4.60%
Transfers Into Level 3	5		25		(42)		21
Long-term debt from Level 3 to Level 2	103		177		527		665
Fair Value Liability, Transfers Into Level 3	(110)		2		(265)		(48)
Deferred fee on stand by letters of credit	40				40						46
Revaluation period					45 days
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Implied volatility percentage					14.00%
Equity Implied volatility					81.00%
Foreign currency correlations					60.00%
Maximum [Member] | Loss Severity Rates [Member] | Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of Inputs					34.00%
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Implied volatility percentage					10.00%
Equity Implied volatility					7.00%
Foreign currency correlations					51.00%
Minimum [Member] | Loss Severity Rates [Member] | Residential Mortgage [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of Inputs					59.00%
Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets	897		1,800		897		1,800
Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets	618		1,400		618		1,400
Credit contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets	213	[1]	301	[1]	213	[1]	301	[1]	225	[1]	571	[1]	921	[1]	1,353	[1]
Transfers Into Level 3	0	[1]	(16)	[1]	46	[1]	(16)	[1]
Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	4,586				4,586						5,383
Trading liabilities	6,595				6,595						8,725
Deposits In Domestic Office [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt from Level 3 to Level 2	79		132		366		607
Fair Value Liability, Transfers Into Level 3	(110)		2		(265)		(41)
Long-term Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets			0	[2]			0	[2]							11	[1]
Transfers Into Level 3							0	[1]
Long-term debt from Level 3 to Level 2	24		45		161		58
Fair Value Liability, Transfers Into Level 3	$ 0		$ 0		$ 0		$ (7)

[1] Level 3 net derivatives included derivative assets of $897 million and derivative liabilities of $618 million as of September 30, 2013 and derivative assets of $1.8 billion and derivative liabilities of $1.4 billion as of September 30, 2012.

[2] Includes Level 3 corporate lending activities risk-managed on a fair value basis for which we have elected the fair value option.