Preferred Stock - Options Exercised (Details) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Preferred stock | ||
| Cash proceeds from exercise of stock options | $ 1,065 | $ 557 |
| Series A convertible preferred stock | ||
| Preferred stock | ||
| Exercise of stock options (in shares) | 185,063 | |
| Cash proceeds from exercise of stock options | $ 89 | |