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Stock-Based Compensation - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2010
2017 Employee Stock Purchase Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Maximum number of shares authorized for issuances   2,000,000    
Price of common stock purchased under ESPP, percent   85.00%    
Maximum percentage of payroll deductions on employee's compensation   15.00%    
Offering period of employee stock purchase plan   6 months    
2007 VI Chip Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Non-qualified stock options       2,984,250
Stock-based compensation expense reversed $ 768,000      
2007 VI Chip Plan [Member] | Cost of Revenues [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Decrease in costs and expenses due to reversal of share-based compensation expense 86,000   $ 86,000  
2007 VI Chip Plan [Member] | Selling, General and Administrative [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Decrease in costs and expenses due to reversal of share-based compensation expense 516,000   516,000  
2007 VI Chip Plan [Member] | Research and Development [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Decrease in costs and expenses due to reversal of share-based compensation expense $ 166,000   $ 166,000