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Stock-Based Compensation - Additional Information (Detail)
3 Months Ended 12 Months Ended
Jan. 01, 2020
shares
Jan. 01, 2019
shares
Mar. 31, 2020
USD ($)
$ / shares
shares
Mar. 31, 2019
USD ($)
Milestone
$ / shares
shares
Mar. 31, 2017
shares
Dec. 31, 2019
shares
Dec. 31, 2018
shares
Sep. 20, 2018
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Stock-based compensation expense | $     $ 31,110,000 $ 44,116,000        
Weighted average grant date fair value per share | $ / shares     $ 46.44 $ 98.23        
Total number of shares reserved     12,685,993          
Common stock available for issuance under stock option plan     3,369,397          
2011 Plan [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Options granted     0          
2014 Stock Option Plan [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Common stock shares annual increase added to plan 2,075,087              
2014 Stock Option Plan [Member] | Maximum [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Percentage of increase on outstanding shares of Common stock           4.00%    
2016 Stock Option Plan [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Total number of shares reserved for issuance               1,200,000
Restricted Stock Units [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Restricted stock units granted     393,811   32,500      
Share based compensation granted under plan vested period         2 years      
Fair value of restricted stock units vested | $       $ 2,000,000.0        
Outstanding and unvested performance restricted stock units     704,631 0   333,243    
Stock-based compensation expense | $       $ 58,000        
Restricted Stock Units [Member] | Restricted Stock Units Vest One Year Anniversary [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Restricted stock units cliff vesting percentage         50.00%      
Restricted stock units vesting period month and year         2018-02      
Restricted Stock Units [Member] | Restricted Stock Units Vest Two Year Anniversary [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Restricted stock units cliff vesting percentage         50.00%      
Restricted stock units vesting period month and year         2019-02      
Performance Restricted Stock Units [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Restricted stock units granted     393,811 354,111     37,800  
Fair value of restricted stock units vested | $     $ 0 $ 0        
Outstanding and unvested performance restricted stock units     704,631          
Total unrecognized stock-based compensation expense | $     $ 61,800,000          
Performance Shares [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Total unrecognized stock-based compensation expense | $     $ 34,100,000          
Options granted   0            
Number of shares outstanding and unvested stock options     457,602          
Performance-Based Stock Options [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Milestones not achieved | Milestone       1        
Stock-based compensation expense | $     $ 0 $ 14,200,000        
Stock Options [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Total unrecognized stock-based compensation expense | $     $ 264,000,000.0          
Options granted     770,860          
Stock-based compensation expense | $     $ 30,218,000 43,564,000        
Weighted average period of unrecognized compensation costs     2 years 4 months 2 days          
Intrinsic value of options exercised | $     $ 100,000 $ 26,700,000        
Total number of shares reserved     8,611,965     8,163,113