Employee Benefits - Net Pension Cost (Benefit) for All Funded and Unfunded Plans (Detail) - Pension Plans [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Interest cost on PBO	$ 10	$ 10	$ 31	$ 30
Expected return on plan assets	(13)	(14)	(39)	(42)
Amortization of losses	4	4	12	13
Settlement loss	0	19	0	19
Net pension/postretirement benefit cost	$ 1	$ 19	$ 4	$ 20