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		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Derivatives, Fair Value
Change in fair value of interest rate swaps hedging long-term debt	$ 39	$ (90)	$ 122	$ (49)
Change in fair value of hedged long-term debt	$ (41)	$ 90	$ (126)	$ 48