Derivative Instruments - Summary of Gains (Losses) Recognized in Earnings for Fair Value Hedges, Other Economic Hedges and Customer-Related Positions (Parenthetical) (Detail) (Asset and Liability Management Positions [Member], Interest Rate Contracts [Member], Fair Value Hedges [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Asset and Liability Management Positions [Member] | Interest Rate Contracts [Member] | Fair Value Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (losses) on items hedged by fair value hedges	$ (33)	$ 2