Derivatives and Hedging Activities - Pre-Tax Net Gains (Losses) on Fair Value Hedges (Detail) (Fair value hedges [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative	$ 109	$ 349
Net Gains (Losses) on Hedged Item	38	(135)
Other Income [Member] | Interest Rate [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative	(52)	163
Net Gains (Losses) on Hedged Item	45	(158)
Other Income [Member] | Foreign exchange [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative	5	(46)
Net Gains (Losses) on Hedged Item	(6)	39
Interest Expense [Member] | Interest Rate [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative	155	220
Interest Expense [Member] | Foreign exchange [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative	1	12
Net Gains (Losses) on Hedged Item	$ (1)	$ (16)