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Stock-Based Compensation - Schedule of Fair Value of Employee and Director Stock Options Estimated Using Weighted Average Assumptions (Details)
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]    
Expected term (in years) 6 years 1 month 6 days 6 years 1 month 6 days
Expected volatility 45.00% 45.90%
Risk-free interest rate 2.40% 2.72%
Dividend yield 0.00% 0.00%