Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts
Movement in Valuation Allowances and Reserves
Balance at Beginning of Period	$ 322	$ 251	$ 200
Charged to Costs and Expenses	205	86	142
Charged to Other Accounts	0	0	0
Deductions	(84)	(15)	(91)
Balance at End of Period	443	322	251
Warranty Reserve
Movement in Valuation Allowances and Reserves
Balance at Beginning of Period	314	675	955
Charged to Costs and Expenses	621	(62)	396
Charged to Other Accounts	0	0	0
Deductions	(155)	(299)	(676)
Balance at End of Period	$ 780	$ 314	$ 675