Schedule II -Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 736
Balance at End of Period	873	$ 736
Reserve for Uncollectible Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	736	820	$ 909
Charged to Costs and Expenses	216	0	0
Deductions	(64)	(44)	(32)
Other	(15)	(40)	(57)
Balance at End of Period	873	736	820
Reserve for Inventory Obsolescence [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	3,803	5,058	4,301
Charged to Costs and Expenses	3,641	1,562	3,204
Deductions	(4,075)	(2,443)	(1,978)
Other	(52)	(374)	(469)
Balance at End of Period	3,317	3,803	5,058
Deferred Tax Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	3,259	2,483	1,758
Charged to Costs and Expenses	857	817	725
Deductions	0	0	0
Other	0	(41)	0
Balance at End of Period	$ 4,116	$ 3,259	$ 2,483