Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts:
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance At Beginning of Year	$ 1,660	$ 601	$ 217
Additions Charged to Operations	1,618	1,136	422
Deductions	(747)	(112)	(38)
Effect of Tax Act	0	0	0
Effect of Change in Foreign Currency Exchange Rates	152	35	0
Balance At End of Year	2,683	1,660	601
Reserve for Excess and Obsolete Inventory:
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance At Beginning of Year	14,039	4,169	5,468
Additions Charged to Operations	2,489	14,797	1,043
Deductions	(4,648)	(4,961)	(2,342)
Effect of Tax Act	0	0	0
Effect of Change in Foreign Currency Exchange Rates	74	34	0
Balance At End of Year	11,954	14,039	4,169
Deferred Tax Asset Valuation Allowance:
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance At Beginning of Year	114,419	94,984	90,774
Additions Charged to Operations	16,364	19,341	17,903
Deductions	0	0	(13,693)
Effect of Tax Act	(38,772)	0	0
Effect of Change in Foreign Currency Exchange Rates	833	94	0
Balance At End of Year	$ 92,844	$ 114,419	$ 94,984