Quantitative Information about Level 3 Fair Value Measurements of Liabilities (Detail) (Fair Value, Measurements, Recurring, USD $) In Millions, unless otherwise specified							6 Months Ended						6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Level 3	Dec. 31, 2011 Level 3	Jun. 30, 2012 Level 3 Trading Liabilities Structured Foreign Exchange Swaptions Option Pricing Model		Jun. 30, 2012 Level 3 Trading Liabilities Structured Foreign Exchange Swaptions Option Pricing Model Minimum		Jun. 30, 2012 Level 3 Trading Liabilities Structured Foreign Exchange Swaptions Option Pricing Model Maximum		Jun. 30, 2012 Level 3 Trading Liabilities Equity Options Option Pricing Model		Jun. 30, 2012 Level 3 Trading Liabilities Equity Options Option Pricing Model Minimum		Jun. 30, 2012 Level 3 Trading Liabilities Equity Options Option Pricing Model Maximum
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair value of liabilities	$ 17,524	$ 18,864	$ 302	$ 314	$ 231	[1]					$ 71	[1]
Correlation risk							0.00%	[1]	25.00%	[1]
Volatility							12.00%	[1]	17.00%	[1]			24.00%	[1]	33.00%	[1]

[1] The option pricing model uses market inputs such as foreign currency exchange rates, interest rates and volatility to calculate the fair value of the option.