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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Movement in Standard Product Warranty Accrual
Balance, beginning of period	$ 1,158	$ 1,384	$ 1,110	$ 1,308
Provision for estimated warranty cost	(261)	383	(18)	622
Warranty expenditures	(43)	(268)	(238)	(431)
Balance, end of period	854	1,499	854	1,499
Less warranty accrual, long-term	194	735	194	735	$ 245
Total warranty accrual, current portion	$ 660	$ 764	$ 660	$ 764	$ 865