Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash and cash equivalents	$ 78,146		$ 78,146		$ 71,029
Fair value of plan assets	5,180		5,180		3,514
Accumulated depreciation of property and equipment	42,109		42,109		39,379
Accumulated amortization of intangible assets	20,309		20,309		18,692
Intangible Assets, Net	6,053		6,053		8,223
Intangible Assets, Accumulated Amortization			2,009
Intangible Assets, Foreign currency translation			161
Amount of goodwill at period end	19,568		19,568		20,083
Net foreign exchange gains (losses)	(375)	$ (638)	(30)	$ (1,256)
Accumulated foreign currency adjustments included in other comprehensive loss amounted	11,810		11,810		9,787
Unrealized loss on marketable securities	$ 905		$ 905		553
Common Stock Options Unvested Restricted Stock and Unvested Performance Units [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of anti-dilutive securities excluded from EPS computation	304	8	256	238
Minimum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life of Intangible assets			7 years
Minimum [Member] | Buildings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of assets			20 years
Minimum [Member] | Computer Equipment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of assets			2 years
Minimum [Member] | Machinery and Equipment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of assets			2 years
Minimum [Member] | Furniture and Fixtures [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of assets			2 years
Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life of Intangible assets			15 years
Maximum [Member] | Buildings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of assets			40 years
Maximum [Member] | Computer Equipment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of assets			10 years
Maximum [Member] | Machinery and Equipment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of assets			10 years
Maximum [Member] | Furniture and Fixtures [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of assets			10 years
Money Market Fund [Member] | Certificates of Deposit [Member] | Level I Instruments [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash and cash equivalents	$ 30,199		$ 30,199		$ 40,760