Derivative Instruments - Summary of Gains (Losses) Recognized in Earnings for Fair Value Hedges, Other Economic Hedges and Customer-Related Positions (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Interest rate contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain losses on items hedged by fair value hedges	$ 2	$ 1
Foreign exchange contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain losses on items hedged by fair value hedges	$ 0	$ (44)