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Commitments And Contingencies - Additional Information (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Commitment And Contingencies [Line Items]      
Rent expenses $ 1,417 $ 1,259 $ 1,094
Minimum      
Commitment And Contingencies [Line Items]      
Royalty expenses percentage 3.00%    
Maximum      
Commitment And Contingencies [Line Items]      
Royalty expenses percentage 3.50%    
IIA      
Commitment And Contingencies [Line Items]      
Maximum royalty payment as percentage of grants received 100.00%    
Aggregate contingent royalty liability (including interest) $ 22,254    
IIA | Cost of Revenue      
Commitment And Contingencies [Line Items]      
Royalty expenses $ 1,016 $ 539 $ 482
IIA | Minimum      
Commitment And Contingencies [Line Items]      
Royalty expenses percentage 3.00%    
IIA | Maximum      
Commitment And Contingencies [Line Items]      
Royalty expenses percentage 3.50%