Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands |
12 Months Ended | |||
|---|---|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Apr. 30, 2012 |
|
| Debt Disclosure [Abstract] | ||||
| Warrants issued (in shares) | 992,000 | |||
| Right to purchase, number of shares per warrant (in shares) | 1 | |||
| Exercise price of warrants (in dollars per warrant) | $ 10.00 | |||
| Warrant liability, at fair value | $ 7,641 | $ 7,296 | $ 5,100 | |
| Warrants exercised (in shares) | 448,000 | 151,000 | 55,000 | |
| Stock issued upon exercise of warrants (in shares) | 289,000 | 91,000 | 32,000 | |
| Fair value of warrant liability reclassified to additional paid in capital upon exercise | $ 8,300 | $ 1,600 | ||
| Change in fair value of warrant liability in current period | $ 4,100 | $ 400 | ||