Nature of Business and Basis of Presentation - New Accounting Pronouncements (Details) - USD ($) $ in Thousands |
Jan. 01, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|---|
| New Accounting Pronouncements or Change in Accounting Principle [Line Items] | |||
| Retained earnings (accumulated deficit) | $ 65,701 | $ 53,200 | |
| Subsequent Event | Minimum | Accounting Standards Update 2016-02 | |||
| New Accounting Pronouncements or Change in Accounting Principle [Line Items] | |||
| Operating lease, liability | $ 4,900 | ||
| Operating lease, right-of-use asset | 5,000 | ||
| Subsequent Event | Maximum | Accounting Standards Update 2016-02 | |||
| New Accounting Pronouncements or Change in Accounting Principle [Line Items] | |||
| Operating lease, liability | 5,200 | ||
| Operating lease, right-of-use asset | 5,500 | ||
| Retained earnings (accumulated deficit) | $ (50) |