Stockholders' Equity - Narrative (Details) $ / shares in Units, $ in Thousands						1 Months Ended	12 Months Ended
	Dec. 16, 2016 USD ($) $ / shares shares	Nov. 04, 2016 shares	Aug. 31, 2016 USD ($) shares	Aug. 30, 2016 USD ($) shares	Jul. 22, 2016	Dec. 16, 2016 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares	Dec. 15, 2016 shares	Jul. 21, 2016 shares	May 25, 2016 shares	Feb. 12, 2016 shares	Feb. 11, 2016 shares
Class of Stock [Line Items]
Common stock and preferred stock, shares authorized (in shares)	50,100,000					50,100,000			20,000,000	20,000,000	100,000,000	100,000,000	24,000,000
Common stock, shares authorized (in shares)	50,000,000					50,000,000	50,000,000	50,000,000				99,900,000
Preferred stock, shares authorized (in shares)	100,000					100,000	100,000	100,000				100,000
Proceeds from issuance of common stock and warrants, net of offering costs | $							$ 0	$ 10,200
Kanis Exchange Agreement
Class of Stock [Line Items]
Issuance of common stock on conversion of debt (in shares)				4,872,032
Extinguishment of debt, amount | $				$ 7,900
Bell Exchange Agreement
Class of Stock [Line Items]
Issuance of common stock on conversion of debt (in shares)				317,950
Extinguishment of debt, amount | $				$ 500
Note Purchase Agreement With Haldor Topsøe
Class of Stock [Line Items]
Issuance of common stock on conversion of debt (in shares)	462,535		308,357
Extinguishment of debt, amount | $	$ 750		$ 500
November 2016 Offering
Class of Stock [Line Items]
Proceeds from issuance of common stock and warrants, net, warrant liability | $						$ 900
Common Stock
Class of Stock [Line Items]
Reverse stock split ratio					0.2
Issuance of common stock on conversion of debt (in shares)								5,961,000
Issuance of stock for settlement of accounts payable (in shares)								81,000
Common Stock | November 2016 Offering
Class of Stock [Line Items]
Proceeds from equity offerings, net of costs (in shares)	4,222,290	949,960				5,172,250
Share price (in dollars per share) | $ / shares	$ 2.00					$ 2.00
Issuance of stock for settlement of accounts payable (in shares)						489,475
Number of securities called by each warrant or right (in shares)	489,475					489,475
Exercise price of warrant or rights (in dollars per share) | $ / shares	$ 2.20					$ 2.20
Proceeds from issuance of common stock and warrants, net of offering costs | $						$ 10,200
Proceeds from issuance of common stock and warrants net equity | $						$ 9,300
Common Stock | Securities Purchase Agreement with MDB Capital Group, LLC
Class of Stock [Line Items]
Share price (in dollars per share) | $ / shares	$ 2					$ 2
Issuance of stock for settlement of accounts payable (in shares)	81,550
Issuance of stock for settlement of accounts payable | $	$ 200