Equity - Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended
	Jan. 06, 2018	Dec. 11, 2017	Dec. 07, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 08, 2017	Jul. 31, 2016
Class of Stock [Line Items]
Common stock, shares authorized (in shares)				150,000,000	150,000,000
Common stock, par value (in dollars per share)			$ 0.001	$ 0.001	$ 0.001
Number of warrants (shares)				27,264,165	6,998,843
Warrants exercise price (usd per share)				$ 2.26	$ 5.98
Number of warrants exercised during the period (shares)				3,531,104
Proceeds from common stock offering, net		$ 9,300		$ 9,749	$ 0
Minimum
Class of Stock [Line Items]
Common stock, shares authorized (in shares)							100,000,000
Maximum
Class of Stock [Line Items]
Common stock, shares authorized (in shares)							150,000,000
Issued in 2017 Common Stock Offering - pre-funded warrants
Class of Stock [Line Items]
Number of warrants (shares)			5,922,208	5,922,208
Issued in 2017 Common Stock Offering - common warrants
Class of Stock [Line Items]
Number of warrants (shares)			13,636,364			410,586
Warrants
Class of Stock [Line Items]
Number of warrants (shares)				20,336,752	0
Number of warrants exercised during the period (shares)				3,506,104
Warrants | Issued in 2017 Common Stock Offering - pre-funded warrants
Class of Stock [Line Items]
Number of warrants (shares)				2,416,104	0
Warrants exercise price (usd per share)				$ 0.01
Warrants | Issued in 2017 Common Stock Offering - common warrants
Class of Stock [Line Items]
Number of warrants (shares)				14,046,950	0
Warrants exercise price (usd per share)			$ 0.77	$ 0.77
Warrant exercise period				5 years
Warrants | Issued in 2017 Common Stock Offering - underwriter warrants
Class of Stock [Line Items]
Number of warrants (shares)				436,364	0
Warrants exercise price (usd per share)				$ 0.9625
Warrant exercise period				5 years
Subsequent Event
Class of Stock [Line Items]
Sale of common stock (in shares)	2,045,454
Purchase price (in usd per share)	$ 0.76
Subsequent Event | Issued in 2017 Common Stock Offering - common warrants
Class of Stock [Line Items]
Number of warrants (shares)	2,045,454
Purchase price (in usd per share)	$ 0.01
Subsequent Event | Warrants | Issued in 2017 Common Stock Offering - common warrants
Class of Stock [Line Items]
Warrants exercise price (usd per share)	$ 0.77
Public Stock Offering
Class of Stock [Line Items]
Sale of common stock (in shares)			7,714,156