Pension and Postretirement Benefit Plans - Additional Information (Detail) - 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]
Net actuarial losses reclassified from accumulated other comprehensive income	$ 1	$ 1	$ 2	$ 1
Contribution to pension and postretirement benefit plans	4		8
Pension and postretirement benefit plans, expected contribution for the remainder of 2015	4		4
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	$ 1	$ 1	$ 1	$ 1