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		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 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	$ (30)	$ (35)	$ (223)	$ (56)
Change in fair value of hedged long-term debt	$ 30	$ 44	$ 220	$ 59