Common Stock Warrants - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended	12 Months Ended
	Aug. 31, 2015	Feb. 28, 2015	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Warrants exercised (in shares)	62,500	27,777	90,277	90,000	0	361,425
Proceeds from exercise of common stock warrants				$ 60	$ 0	$ 286