Stockholders' Equity - Common Stock (Details) $ / shares in Units, $ in Thousands			12 Months Ended
	Jul. 21, 2017 shares	Jun. 30, 2017 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) vote $ / shares shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($)	Jun. 29, 2017 shares	Jun. 19, 2017 $ / shares shares
Subsidiary, Sale of Stock [Line Items]
Number of votes per common share | vote			1
Common stock, par value (in dollars per share) | $ / shares		$ 0.0001	$ 0.0001	$ 0.0001
Proceeds from common stock issuance | $			$ 11,952	$ 0	$ 0
Common Stock Warrant
Subsidiary, Sale of Stock [Line Items]
Common stock, par value (in dollars per share) | $ / shares			$ 0.0001
Common Stock Warrant | Soryn HLDR
Subsidiary, Sale of Stock [Line Items]
Exercise price (in dollars per share) | $ / shares			$ 3.18				$ 3.18
Exercise period			3 years
Underwriting Agreement
Subsidiary, Sale of Stock [Line Items]
Proceeds from common stock issuance | $		$ 10,400
Over-allotment option
Subsidiary, Sale of Stock [Line Items]
Proceeds from common stock issuance | $		$ 1,600
Common Stock
Subsidiary, Sale of Stock [Line Items]
New share issues (in shares) | shares			4,140,000
Common Stock | Common Stock Warrant | Soryn HLDR
Subsidiary, Sale of Stock [Line Items]
Common stock warrant purchased (in shares) | shares		2,400,000				2,000,000	2,355,506
Common Stock | Underwriting Agreement
Subsidiary, Sale of Stock [Line Items]
New share issues (in shares) | shares		3,600,000
Price per share (in dollars per share) | $ / shares		$ 3.15
Price per share, net proceeds (in dollars per share) | $ / shares		$ 2.90
Common Stock | Over-allotment option
Subsidiary, Sale of Stock [Line Items]
New share issues (in shares) | shares		540,000
Common Stock | Over-allotment option | Common Stock Warrant | Soryn HLDR
Subsidiary, Sale of Stock [Line Items]
Number of share called by warrant, increase (in shares) | shares	50,000