Fair Value Measurement- Quantitative Information about Level 3 Fair Value Measurements of Liabilities (Detail) (Fair Value, Measurements, Recurring, Level 3, USD $) In Millions, unless otherwise specified					9 Months Ended				9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Trading Liabilities Structured Foreign Exchange Swaptions Option Pricing Model		Sep. 30, 2014 Trading Liabilities Structured Foreign Exchange Swaptions Option Pricing Model Minimum	Sep. 30, 2014 Trading Liabilities Structured Foreign Exchange Swaptions Option Pricing Model Maximum	Sep. 30, 2014 Trading Liabilities Equity Options Option Pricing Model		Sep. 30, 2014 Trading Liabilities Equity Options Option Pricing Model Minimum	Sep. 30, 2014 Trading Liabilities Equity Options Option Pricing Model Maximum
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair value of liabilities	$ 26	$ 75	$ 23	[1]			$ 3	[1]
Correlation risk (percent)					0.00%	25.00%
Volatility (percent)					11.00%	18.00%			21.00%	22.00%

[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.