Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	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	$ 4,409	$ 7,641		$ 5,100
Warrants exercised (in shares)	18,000	448,000
Stock issued upon exercise of warrants (in shares)	11,000	289,000
Fair value of warrant liability reclassified to additional paid in capital upon exercise	$ 300	$ 8,300
Change in fair value of warrant liability in current period	$ 100	$ 4,100	$ 400