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Stock-Based Compensation - Assumptions Used For Stock Options (Details) - Stock option awards - $ / shares
9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Weighted average grant-date fair value per share (in dollars per share) $ 4.47 $ 7.74
Expected term (in years) 6 years 6 years
Expected stock volatility 46.00% 41.00%
Dividend yield 0.00% 0.00%
Risk-free interest rate 2.30% 2.60%