Quarterly report pursuant to Section 13 or 15(d)

Stock Plans - Additional Information (Detail)

v3.19.2
Stock Plans - Additional Information (Detail) - USD ($)
 6 Months Ended
Jan. 31, 2019
Jun. 30, 2019
Jun. 30, 2018
Dec. 31, 2018
Class of Stock [Line Items]        
Accrued employee contributions   $ 2,819,000   $ 6,570,000
Employee Stock Purchase Plan [Member]        
Class of Stock [Line Items]        
Common stock were purchased under ESPP 64,967      
Accrued employee contributions   $ 277,000    
Timebased Stock Option [Member]        
Class of Stock [Line Items]        
Options granted   555,346    
Vesting period   4 years    
Performance-based Stock Options [Member]        
Class of Stock [Line Items]        
Options granted   1,545,849    
Vesting period   30 days    
Options exercise price   $ 5.74    
Total grant date fair value of stock options granted   $ 3,970,000    
Weighted Average Grant Date Fair Value, Granted   $ 2.57 $ 9.59  
Expected term (in years)   6 years 4 months 24 days    
Cost of share-based compensation awards, recognition period   3 years 8 months 12 days    
Total grant date fair value of stock options vested   $ 0 $ 0  
Unrecognized compensation expense related to stock options   $ 26,231,000    
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   $ 246,000    
Cost of share-based compensation awards, recognition period   1 year 3 months 18 days    
Restricted Stock Units [Member]        
Class of Stock [Line Items]        
Unrecognized cost of share-based compensation awards   $ 950,000    
Cost of share-based compensation awards, recognition period   1 year 2 months 12 days    
Stock Options [Member]        
Class of Stock [Line Items]        
Options granted   555,346    
Options exercise price   $ 5.98    
Weighted Average Grant Date Fair Value, Granted   $ 3.72 $ 9.73  
Cost of share-based compensation awards, recognition period   2 years 1 month 6 days    
Total grant date fair value of stock options vested   $ 5,465,000 $ 4,626,000  
Unrecognized compensation expense related to stock options   13,924,000    
Aggregate intrinsic value of the options exercised   $ 177,000 $ 1,698,000