Warrants - Calculated Aggregated Fair Values and Assumptions (Details) - Warrant Liability $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares
Class of Warrant or Right [Line Items]
Calculated aggregate value | $	$ 152	$ 1,073
Weighted average exercise price per share of warrant (usd per share)	$ 22.50	$ 30.10
Closing price per share of common stock (usd per share)	$ 1.50	$ 3.20
Volatility
Class of Warrant or Right [Line Items]
Warrant measurement input	0.941	0.922
Measurement Input, Expected Term
Class of Warrant or Right [Line Items]
Weighted average remaining expected life	2 years 8 months	3 years 4 months
Risk-free interest rate (term structure)
Class of Warrant or Right [Line Items]
Warrant measurement input	0.0245	0.0200
Dividend yield
Class of Warrant or Right [Line Items]
Warrant measurement input	0.0000	0.0000