Changes in Initial Product Warranty Accrual and Expenses Under Initial and Extended Warranties (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Movement in Standard Product Warranty Accrual
Initial warranty accrual, beginning balance	$ 1,919	$ 1,997	$ 2,188	$ 1,449
Provision for estimated warranty cost	282	608	379	1,604
Warranty expenditures	(224)	(270)	(590)	(718)
Initial warranty accrual, ending balance	1,977	2,335	1,977	2,335
Less warranty accrual, long-term	955	1,059	955	1,059	$ 843
Total warranty accrual, current portion	$ 1,022	$ 1,276	$ 1,022	$ 1,276	$ 1,345