Stock-Based Compensation - Schedule of Assumptions Used in Black-Scholes Option-Pricing Method (Details) - $ / shares |
3 Months Ended | 9 Months Ended | 12 Months Ended | |||
|---|---|---|---|---|---|---|
Sep. 30, 2019 |
Sep. 30, 2018 |
Sep. 30, 2019 |
Sep. 30, 2018 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Expected dividend yield | 0.00% | 0.00% | 0.00% | 0.00% | 0.00% | 0.00% |
| Expected stock-price volatility, minimum | 69.00% | 48.89% | 46.33% | 46.47% | 46.47% | 53.08% |
| Expected stock-price volatility, maximum | 69.38% | 50.22% | 69.38% | 53.11% | 53.11% | 54.08% |
| Risk-free interest rate, minimum | 1.47% | 2.78% | 1.47% | 2.46% | 2.46% | 1.89% |
| Risk-free interest rate, maximum | 1.54% | 3.07% | 2.60% | 3.07% | 3.07% | 2.58% |
| Expected average term of options | 10 years | |||||
| Stock price | $ 1.04 | |||||
| Minimum [Member] | ||||||
| Expected average term of options | 5 years | 7 years | 5 years | 5 years | 5 years | |
| Stock price | $ 1.85 | $ 0.60 | $ 1.85 | $ 1.85 | $ 0.30 | |
| Maximum [Member] | ||||||
| Expected average term of options | 7 years | 10 years | 7 years | 10 years | 10 years | |
| Stock price | $ 2.22 | $ 1.04 | $ 3.40 | $ 3.40 | $ 3.48 | |