Derivatives and Hedging Activities - Pre-Tax Net Gains (Losses) on Fair Value Hedges (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative	$ 124	$ (93)
Net Gains (Losses) on Hedged Item	(5)	222
Other Income [Member] | Interest Rate [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative	7	(222)
Net Gains (Losses) on Hedged Item	(5)	222
Interest Expense [Member] | Interest Rate [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) on Derivative	$ 117	$ 129