Change in the Fair Value for Interest Rate Contracts and the Related Hedged Items (Detail) (Fair Value Hedging, Interest Rate Contract, Interest Expense, Long-Term Debt, USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Fair Value Hedging | Interest Rate Contract | Interest Expense, Long-Term Debt
Derivatives, Fair Value
Change in fair value of interest rate swaps hedging long-term debt	$ (127)	$ 78	$ (194)	$ (22)
Change in fair value of hedged long-term debt	$ 125	$ (78)	$ 191	$ 14