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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Movement in Standard Product Warranty Accrual
Initial warranty accrual, beginning balance	$ 1,997	$ 1,255	$ 1,449	$ 1,096
Provision for estimated warranty cost	608	310	1,604	919
Warranty expenditures	(270)	(199)	(718)	(649)
Initial warranty accrual, ending balance	2,335	1,366	2,335	1,366
Less warranty accrual, long-term	1,059	367	1,059	367	$ 519
Total warranty accrual, current portion	$ 1,276	$ 999	$ 1,276	$ 999	$ 930