Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Reduction in trading revenue	$ 47
Derivative, Number of Instruments Held	30
Fair Value Inputs, Loss Severity	180.00%
Long-term debt from Level 3 to Level 2	911	3,296
Transfer of credit derivatives from Level 3 to level 2		62
Deferred fee on stand by letters of credit	46	44
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Interest in Hedge Finds, Percentage Discounted	60.00%
Derivative Instrument, Foreign Currency, Implied Volatility Percentage	20.90%
Derivative Instrument, Equity, Implied Volatility	104.00%
Derivative Instruments, Foreign Currency, Correlations of a Group, Percentage	64.00%
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Interest in Hedge Finds, Percentage Discounted	50.00%
Derivative Instrument, Foreign Currency, Implied Volatility Percentage	1.60%
Derivative Instrument, Equity, Implied Volatility	6.00%
Derivative Instruments, Foreign Currency, Correlations of a Group, Percentage	56.00%
Loss Severity Rates [Member] | Residential Mortgage [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate	28.70%
Loss Severity Rates [Member] | Residential Mortgage [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate	59.80%
Derivatives [Member] | Deposits In Domestic Offices [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt from Level 3 to Level 2	848	2,700
Derivatives [Member] | Long-term Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt from Level 3 to Level 2	$ 63	$ 554