Derivatives and Hedging Activities - Pre-Tax Net Gains (Losses) on Fair Value Hedges (Detail) (Fair Value Hedges [Member], USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative	$ (90)	$ 82
Net Gains (Losses) on Hedged Item	155	3
Other Income [Member] | Interest Rate [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative	(156)	(13)
Net Gains (Losses) on Hedged Item	155	10
Other Income [Member] | Foreign Exchange [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative		5
Net Gains (Losses) on Hedged Item		(6)
Interest Expense [Member] | Interest Rate [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative	66	89
Interest Expense [Member] | Foreign Exchange [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative		1
Net Gains (Losses) on Hedged Item		$ (1)