Fair Value Measurements - Fair Value Hierarchy Table (Details) - Recurring basis - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Liabilities measured at fair value
Total	$ 176	$ 1,773
Tradable warrants
Liabilities measured at fair value
Warrant liability	176	1,755
Non-tradable warrants
Liabilities measured at fair value
Warrant liability		18
Level 1
Liabilities measured at fair value
Total	176	1,755
Level 1 | Tradable warrants
Liabilities measured at fair value
Warrant liability	$ 176	1,755
Level 3
Liabilities measured at fair value
Total		18
Level 3 | Non-tradable warrants
Liabilities measured at fair value
Warrant liability		$ 18