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Significant Accounting Policies - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Schedule Of Significant Accounting Policies Summary [Line Items]      
Depreciation expense $ 14.0 $ 15.1 $ 16.4
Forward Contracts | Minimum      
Schedule Of Significant Accounting Policies Summary [Line Items]      
Foreign exchange contract term 1 month    
Forward Contracts | Maximum      
Schedule Of Significant Accounting Policies Summary [Line Items]      
Foreign exchange contract term 18 months    
Customer Concentration Risk | Accounts Receivable      
Schedule Of Significant Accounting Policies Summary [Line Items]      
Percentage of major customer net receivables to total receivables (as a percent) 59.00% 64.00%