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Property, Plant and Equipment - Additional Information (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Property, Plant and Equipment [Line Items]      
Depreciation of property, plant and equipment $ 66,122 $ 64,782 $ 68,181
Machinery and equipment 647,961 601,835  
Accumulated depreciation 646,045 595,147  
Test Systems Leased By Customers      
Property, Plant and Equipment [Line Items]      
Machinery and equipment 18,100 19,400  
Accumulated depreciation $ 13,700 $ 10,500