Derivative Financial Instruments - Gains and Losses on Derivative Instruments Held For Other Purpose (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	$ 165	$ 388
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	161	349
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	214	109
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Foreign exchange contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	12	(1)
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Equity contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	(49)	257
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Precious metals contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	0	1
Other Income [Member] | Credit contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	$ (12)	$ 22