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Share-Based Compensation - Narrative (Details) - USD ($)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
May 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Grants during period (shares) 2,310,994      
Exercise price required percentage of fair market value 100.00%      
Award vesting period 4 years      
Intrinsic value of options exercised $ 38,600,000 $ 18,800,000 $ 300,000  
Cash received from exercise of stock options 8,500,000 9,700,000 400,000  
Fair value of options vested 20,400,000 8,200,000 10,600,000  
Capitalized costs 0 0 0  
Tax benefit from compensation expense 0 $ 0 $ 0  
Compensation cost not yet recognized $ 77,400,000      
Compensation cost not yet recognized, period for recognition 1 year 3 months 18 days      
2013 Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Additional shares authorized (shares) 2,500,000      
Authorized amount for issuance (shares) 2,200,000      
Stock option contractual terms 10 years      
Stock authorized for purchase (shares)       $ 25,000
Purchase discount (as a percent)       85.00%
Stock reserved for future issuance (shares)       300,000
Issuance of common stock from ESPP (shares) 157,128      
Stock Option Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Authorized amount for issuance (shares) 0      
Stock option contractual terms 7 years      
Inducement Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based Payment Arrangement, Option, Exercise Price Range, Shares Outstanding 417,343      
Grants during period (shares) 0