Preferred Stock and Common Stock Warrants - Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		2 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Aug. 31, 2018	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2018
Warrants
Term of warrants (in years)			3 years
Number of trading days to exercise prior to expiration term			60 days
Number of consecutive trading days to exercise warrants prior to expiration term			90 days
Minimum conversion price percentage			175.00%
Gain (loss) recognized on revalued warrants			$ 83	$ 83	$ 83
Series A Warrants | HGC
Warrants
Basis of acquired diluted common stock - warrants rights (as a percent)		0.50%
Strike price of warrants (in dollars per share)		$ 0.01
Series A Warrants | Backstop Agreements | Fund Purchaser
Warrants
Basis of acquired diluted common stock - warrants rights (as a percent)		0.21%
Strike price of warrants (in dollars per share)		$ 0.01
Series B Warrants
Warrants
Denominator of aggregate purchase price	$ 35,000
Preferred stock warrants multiplier	0.50%
Strike price of warrants (in dollars per share)	$ 0.01		$ 0.01	$ 0.01	$ 0.01