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], Fair Value Hedges [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain losses on items hedged by fair value hedges	$ (27)	$ 8	$ (3)
Foreign Exchange Cross-Currency Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain losses on items hedged by fair value hedges			$ (44)