Derivative Financial Instruments - Gains and Losses on Derivative Instruments Held For Other Purpose (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	$ 944	$ 391
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	845	337	758
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	439	(303)
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	20	(70)
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	442	774
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	11	0
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Credit contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	1	2
Residential mortgage banking revenue [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	(1)	(5)
Other Income [Member] | Credit contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	$ 32	$ (7)