Employee Benefits - Net Pension Cost (Benefit) for Funded and Unfunded Plans (Detail) - Pension Plans [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Interest cost on PBO	$ 10	$ 12	$ 30	$ 36
Expected return on plan assets	(14)	(17)	(42)	(51)
Amortization of losses	4	4	13	12
Settlement loss	19	20	19	20
Net benefit cost	$ 19	$ 19	$ 20	$ 17