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Change in the Fair Value for Interest Rate Contracts and the Related Hedged Items (Detail) (Fair Value Hedging, Interest Rate Contract, USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Interest Expense Long Term Debt [Member]
     
Derivatives, Fair Value [Line Items]      
Change in fair value of interest rate swaps hedging long-term debt $ 220 $ 167 $ (548)
Change in fair value of hedged long-term debt (227) (168) 538
Interest Expense Deposits [Member]
     
Derivatives, Fair Value [Line Items]      
Change in fair value of interest rate swaps hedging long-term debt   6 4
Change in fair value of hedged long-term debt   $ (6) $ (3)