Quarterly report pursuant to Section 13 or 15(d)

Stock Plans - Additional Information (Detail)

v3.19.3
Stock Plans - Additional Information (Detail) - USD ($)
 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Class of Stock [Line Items]      
Accrued employee contributions $ 2,330,000   $ 6,570,000
Employee Stock Purchase Plan [Member]      
Class of Stock [Line Items]      
Common stock were purchased under ESPP 129,514    
Accrued employee contributions $ 118,000    
Timebased Stock Option [Member]      
Class of Stock [Line Items]      
Options granted 607,596    
Vesting period 4 years    
Performance-based Stock Options [Member]      
Class of Stock [Line Items]      
Options granted 1,619,175    
Vesting period 30 days    
Options exercise price $ 5.69    
Total grant date fair value of stock options granted $ 4,122,000    
Weighted Average Grant Date Fair Value, Granted $ 2.55 $ 9.59  
Expected term (in years) 6 years 4 months 24 days    
Cost of share-based compensation awards, recognition period 3 years 6 months    
Total grant date fair value of stock options vested $ 0 $ 0  
Unrecognized compensation expense related to stock options $ 24,001,000    
Performance-based Stock Options [Member] | Tranche 1 [Member]      
Class of Stock [Line Items]      
Options exercise price $ 49.15    
Performance-based Stock Options [Member] | Tranche 2 [Member]      
Class of Stock [Line Items]      
Options exercise price 98.31    
Performance-based Stock Options [Member] | Tranche 3 [Member]      
Class of Stock [Line Items]      
Options exercise price $ 196.62    
Restricted Stock [Member]      
Class of Stock [Line Items]      
Unrecognized cost of share-based compensation awards $ 199,000    
Cost of share-based compensation awards, recognition period 1 year 1 month 6 days    
Restricted Stock Units [Member]      
Class of Stock [Line Items]      
Unrecognized cost of share-based compensation awards $ 753,000    
Cost of share-based compensation awards, recognition period 1 year    
Stock Options [Member]      
Class of Stock [Line Items]      
Options granted 607,596    
Options exercise price $ 5.86    
Weighted Average Grant Date Fair Value, Granted $ 3.65 $ 7.90  
Cost of share-based compensation awards, recognition period 2 years    
Total grant date fair value of stock options vested $ 8,056,000 $ 6,711,000  
Unrecognized compensation expense related to stock options 11,235,000    
Aggregate intrinsic value of the options exercised $ 183,000 $ 1,964,000