Stock-based Compensation - Fair Value of Options Granted Using the Black-Scholes Pricing Model (Details) - Stock options |
3 Months Ended | 9 Months Ended | ||
---|---|---|---|---|
Sep. 30, 2018 |
Sep. 30, 2017 |
Sep. 30, 2018 |
Sep. 30, 2017 |
|
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Expected volatility rate | 47.80% | |||
Volatility, minimum | 42.40% | 41.70% | 38.60% | |
Volatility, maximum | 44.10% | 44.20% | 47.80% | |
Risk free interest rate | 2.80% | |||
Risk-free interest rate, minimum | 1.90% | 1.90% | 2.60% | |
Risk-free interest rate, maximum | 2.10% | 2.20% | 2.90% | |
Expected term (in years) | 6 years 1 month 6 days | 6 years 3 months | ||
Dividend rate | 0.00% | 0.00% | 0.00% | 0.00% |
Minimum | ||||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Expected term (in years) | 5 years 6 months | 5 years 6 months | 5 years 6 months | |
Maximum | ||||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Expected term (in years) | 6 years 3 months 18 days | 6 years 3 months 18 days |