Pensions and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Detail) (Postretirement benefits [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Postretirement benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1		$ 1
Interest cost		1	2	3
Amortization of transition obligation	1	1	2	2
Net periodic pension cost (income)	$ 2	$ 2	$ 5	$ 5