Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Common stock, par value (usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	26,259,254	22,167,529
Common stock, shares outstanding (in shares)	26,259,254	22,167,529
Preferred stock, par value (usd per share)	$ 0.0001
Preferred stock, shares authorized (in shares)	8,000,000
Series C-1 Convertible Preferred Stock [Member]
Preferred stock, par value (usd per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	11,000	11,000
Preferred stock, shares issued (in shares)	3,906	3,906
Preferred stock, shares outstanding (in shares)	3,906	3,906
Liquidation preference	$ 3,906	$ 3,906
Series F Convertible Preferred Stock [Member]
Preferred stock, par value (usd per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	10,000	10,000
Preferred stock, shares issued (in shares)	2,737	2,737
Preferred stock, shares outstanding (in shares)	2,737	2,737
Liquidation preference	$ 2,737	$ 2,737