Annual report pursuant to Section 13 and 15(d)

Commitments and Contingencies - Additional Information (Detail)

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Commitments and Contingencies - Additional Information (Detail)
 1 Months Ended 12 Months Ended
Feb. 28, 2018
Mar. 31, 2015
USD ($)
Feb. 28, 2015
Dec. 31, 2017
USD ($)
ft²
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Commitment And Contingencies [Line Items]            
Area of corporate headquarters and manufacturing facility | ft²       57,000    
Extended lease term   Apr. 30, 2020        
Provisions for tenant improvement allowance, maximum   $ 398,000        
Capital lease agreement term for information technology equipment     30 months      
Future minimum lease payments under capital lease, borrowing rate       1.60%    
Capital lease prepayment       $ 14,000,000    
Future minimum lease payments under capital lease including net minimum lease payment for year ended December 31, 2018       0    
Capital lease obligation, long-term       0    
Rent expense       1,000,000 $ 1,000,000 $ 1,000,000
Purchase commitments pending       10,300,000    
Employee Arrangements and Other Compensation            
Commitment And Contingencies [Line Items]            
Change in control, if occurs, may require severance benefits payable       1,700,000 1,300,000  
Accrued for performance bonuses       $ 67,000 $ 67,000  
Subsequent Event            
Commitment And Contingencies [Line Items]            
Capital lease agreement extended additional lease term for information technology equipment 18 months