Changes in Initial Product Warranty Accrual and Expenses Under Initial and Extended Warranties (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Movement in Standard Product Warranty Accrual
Initial warranty accrual, beginning balance	$ 2,060	$ 1,667	$ 2,188	$ 1,449
Provision for estimated warranty cost	36	545	97	996
Warranty expenditures	(177)	(215)	(366)	(448)
Initial warranty accrual, ending balance	1,919	1,997	1,919	1,997
Less warranty accrual, long-term	866	868	866	868	$ 843
Total warranty accrual, current portion	$ 1,053	$ 1,129	$ 1,053	$ 1,129	$ 1,345