Derivatives (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	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Derivatives, Fair Value
Change in fair value of interest rate swaps hedging long-term debt	$ (19)	$ 64	$ 103	$ 15
Change in fair value of hedged long-term debt	$ 17	$ (65)	$ (109)	$ (18)