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Stock-Based Compensation - Stock Options and Restricted Stock Units Activity (Details) - USD ($)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Stock Options      
Stock Options      
Outstanding beginning of period (in shares) 1,129,463    
Options granted (in shares) 50,000 0  
Options exercised (in shares) (539,853)    
Options cancelled (in shares) (750)    
Outstanding end of period (in shares) 638,860 1,129,463  
Exercisable (in shares) 586,985    
Weighted-Average Exercise Price Per Share      
Outstanding beginning of period (in dollars per share) $ 2.29    
Options granted (in dollars per share) 21.13    
Options exercised (in dollars per share) 1.60    
Options cancelled (in dollars per share) 26.33    
Outstanding end of period (in dollars per share) 4.31 $ 2.29  
Exercisable (in dollars per share) $ 2.84    
Weighted-Average Remaining Contractual Life (Yrs.)      
Weighted-Average Remaining Contractual Life, Outstanding (in years) 4 years 3 months 18 days 4 years 2 months 12 days  
Weighted-Average Remaining Contractual Life, Exercisable (in years) 3 years 10 months 24 days    
Aggregate Intrinsic Value      
Outstanding beginning of period (in dollars) $ 25,052,908    
Outstanding end of period (in dollars) 12,192,995 $ 25,052,908  
Exercisable (in dollars) 12,067,647    
Total unrecognized compensation expense $ 538,991    
Weighted-average period expected to be recognized 3 years 7 months 6 days    
Total grant date fair value of stock options vested during the period $ 101,387    
Total intrinsic value of options exercised $ 11,870,492 $ 6,071,319 $ 268,053
Weighted-average grant-date fair value of options granted (in dollars per share) $ 11.84   $ 11.10
Summary of weighted average assumptions used to estimate the fair value of stock option grants      
Volatility (as a percent) 59.10%   92.00%
Expected term (years) 6 years 3 months 18 days 0 years 6 years 3 months 18 days
Risk- free interest rate (as a percent) 1.50%   1.40%
Dividend yield (as a percent) 0.00%   0.00%
Restricted Stock Units      
Aggregate Intrinsic Value      
Weighted-average period expected to be recognized 3 years 1 month 6 days