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Stock-Based Compensation - Restricted Stock and Stock Options (Details) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Weighted Average Grant Date Fair Value      
Compensation expense $ 23,156 $ 27,243  
Restricted Stock      
Changes in unvested restricted stock      
Unvested restricted shares, beginning of period (in shares) 581,408    
Issued (in shares) 364,549    
Vested (in shares) (304,638)    
Forfeited (in shares) (133,869)    
Unvested restricted shares, end of period(in shares) 507,450 581,408  
Weighted Average Grant Date Fair Value      
Balance, beginning of period $ 24.03    
Issued (in dollars per share) 29.57    
Vested (in dollars per share) 23.37    
Forfeited (in dollars per share) 24.72    
Balance, ending of period $ 27.35 $ 24.03  
Unrecognized stock-based compensation expense $ 11,900    
Period for recognition 2 years 8 months 12 days    
Restricted Stock | Employees      
Weighted Average Grant Date Fair Value      
Compensation expense $ 2,800 $ 4,700 $ 0
Restricted Stock | Non-employees      
Weighted Average Grant Date Fair Value      
Compensation expense 1,600 $ 1,600 2,400
Stock options      
Weighted Average Grant Date Fair Value      
Unrecognized stock-based compensation expense $ 40,400    
Period for recognition 2 years 8 months 12 days    
Changes in unvested stock options      
Outstanding, beginning of period (in shares) 4,358,291    
Granted (in shares) 1,721,748    
Exercised (in shares) (964,412)    
Cancelled (in shares) (1,203,370)    
Outstanding, end of period (in shares) 3,912,257 4,358,291  
Exercisable (in shares) 1,463,668    
Outstanding, beginning of period (in dollars per share) $ 25.40    
Granted (in dollars per share) 30.44    
Exercised (in dollars per share) 20.22    
Cancelled (in dollars per share) 30.72    
Outstanding, end of period (in dollars per share) 27.26 $ 25.40  
Exercisable (in dollar per share) $ 24.05    
Remaining contractual life 7 years 10 months 24 days 7 years 4 months 24 days  
Exercisable, remaining contractual life 6 years 9 months 18 days    
Aggregate intrinsic value $ 167,640 $ 26,060  
Exercisable, aggregated intrinsic value 67,413    
Employee and Consultant Options      
Changes in unvested stock options      
Intrinsic value of options exercised $ 15,600 $ 14,600 $ 15,900
Weighted average fair value of options granted (per share) $ 16.60 $ 15.67 $ 24.91
Employee and Consultant Options | Employees and directors      
Weighted Average Grant Date Fair Value      
Compensation expense $ 16,100 $ 18,100 $ 19,900