Change in the Fair Value for Interest Rate Contracts and the Related Hedged Items (Detail) (Fair Value Hedging, Interest Rate Contract, USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Interest Expense Long Term Debt [Member]
Derivatives, Fair Value [Line Items]
Change in fair value of interest rate swaps hedging long-term debt	$ 258	$ 123	$ 238	$ 408
Change in fair value of hedged long-term debt	(255)	(122)	(242)	(409)
Interest Expense Deposits [Member]
Derivatives, Fair Value [Line Items]
Change in fair value of interest rate swaps hedging long-term debt		1		6
Change in fair value of hedged long-term debt		$ (1)		$ (6)