Product Warranty Accrual Included in Other Accrued Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Balance as of January 1	$ 14,886	$ 11,437
Provision for warranties issued in current year	2,766	2,168
Walker acquisition	0	3,887
Provisions for pre-existing warranties	650	0
Payments	(2,879)	(1,922)
Balance as of June 30	$ 15,423	$ 15,570