Derivatives and Hedging Activities - Pre-Tax Net Gains (Losses) on Fair Value Hedges (Detail) (Fair value hedges [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative	$ (5)	$ (4)
Net Gains (Losses) on Hedged Item	38	46
Other Income [Member] | Interest Rate [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative	(38)	(55)
Net Gains (Losses) on Hedged Item	38	52
Other Income [Member] | Foreign exchange [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative		5
Net Gains (Losses) on Hedged Item		(5)
Interest Expense [Member] | Interest Rate [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative	33	45
Interest Expense [Member] | Foreign exchange [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative		1
Net Gains (Losses) on Hedged Item		$ (1)