Quarterly report pursuant to Section 13 or 15(d)

Stock Plans - Additional Information (Detail)

v3.19.1
Stock Plans - Additional Information (Detail) - USD ($)
 3 Months Ended
Jan. 31, 2019
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Class of Stock [Line Items]        
Accrued employee contributions   $ 3,247,000   $ 6,570,000
Employee Stock Purchase Plan [Member]        
Class of Stock [Line Items]        
Common stock were purchased under ESPP 64,967      
Accrued employee contributions   $ 141,000    
Timebased Stock Option [Member]        
Class of Stock [Line Items]        
Options granted   432,400    
Vesting period   4 years    
Expected term (in years)   6 years    
Performance-based Stock Options [Member]        
Class of Stock [Line Items]        
Options granted   1,449,102    
Vesting period   30 days    
Options exercise price   $ 5.67    
Total grant date fair value of stock options granted   $ 3,674,000    
Weighted Average Grant Date Fair Value, Granted   $ 2.54    
Expected term (in years)   6 years 4 months 24 days    
Cost of share-based compensation awards, recognition period   3 years 10 months 24 days    
Total grant date fair value of stock options vested   $ 0    
Unrecognized compensation expense related to stock options   $ 28,247,000    
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   $ 240,000    
Cost of share-based compensation awards, recognition period   1 year 9 months 18 days    
Restricted Stock Units [Member]        
Class of Stock [Line Items]        
Unrecognized cost of share-based compensation awards   $ 450,000    
Cost of share-based compensation awards, recognition period   7 months 6 days    
Stock Options [Member]        
Class of Stock [Line Items]        
Options granted   432,400    
Options exercise price   $ 5.66    
Weighted Average Grant Date Fair Value, Granted   $ 3.55 $ 7.91  
Cost of share-based compensation awards, recognition period   2 years 2 months 12 days    
Total grant date fair value of stock options vested   $ 2,718,000 $ 1,761,000  
Unrecognized compensation expense related to stock options   16,883,000    
Aggregate intrinsic value of the options exercised   $ 74,000 $ 692,000