Employee Stock Options (Details) - Employee Stock Option [Member] |
3 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|
Mar. 31, 2019 |
Mar. 31, 2018 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Summary of assumptions used to estimate fair value of stock options granted | ||||
| Expected dividend yield | 0.00% | 0.00% | 0.00% | 0.00% |
| Expected volatility | 90.00% | |||
| Risk-free interest rate | 2.49% | |||
| Expected life of options | 4 years | 4 years | ||
| Minimum [Member] | ||||
| Summary of assumptions used to estimate fair value of stock options granted | ||||
| Expected volatility | 83.00% | 80.00% | 82.00% | |
| Risk-free interest rate | 2.40% | 2.41% | 1.50% | |
| Expected life of options | 2 years 6 months | 2 years 6 months | ||
| Maximum [Member] | ||||
| Summary of assumptions used to estimate fair value of stock options granted | ||||
| Expected volatility | 86.00% | 96.00% | 101.00% | |
| Risk-free interest rate | 2.47% | 2.93% | 2.62% | |
| Expected life of options | 3 years | 4 years | ||