Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	June Offering [Member]	June Purchase Agreement [Member]	Common Stock [Member]	Common Stock [Member] Securities Purchase Agreement [Member]	Common Stock [Member] June Purchase Agreement [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] June Offering [Member]	Additional Paid-In Capital [Member] Securities Purchase Agreement [Member]	Additional Paid-In Capital [Member] June Purchase Agreement [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]
Stockholders Equity, Beginning Balance at Dec. 31, 2016	$ 22,198			$ 44			$ 173,723				$ (151,550)	$ (19)
Stockholders Equity, Beginning Balance, Shares at Dec. 31, 2016				2,224,384
Issuance of shares related to employee stock purchase plan	24						24
Issuance of shares related to employee stock purchase plan, Shares				1,964
Stock-based compensation	1,474						1,474
Other comprehensive income	18											18
Exchange of membership interest in unconsolidated entity for common stock				$ (2)			2
Exchange of membership interest in unconsolidated entity for common stock, Shares				(92,194)
Net loss	(15,707)										(15,707)
Stockholders Equity, Ending Balance at Dec. 31, 2017	8,007			$ 42			175,223				(167,257)	(1)
Stockholders Equity, Ending Balance, Shares at Dec. 31, 2017				2,134,153
Impact of adoption of Topic 606 (Note 5) | Topic 606 [Member]	2,371										2,371
Issuance of shares related to employee stock option exercises	$ 963						963
Issuance of shares related to employee stock option exercises, Shares	44,354			44,354
Issuance of shares related to employee stock purchase plan	$ 6						6
Issuance of shares related to employee stock purchase plan, Shares				1,122
Issuance of shares			$ 4,978		$ 1	$ 2			$ (1)	$ 4,976
Issuance of shares, Shares					1,201,634	1,392,345
Issuance of placement agent warrants	526	$ 427					526	$ 427
Common stock adjustment feature	8,378						8,378
Offering costs related to June Offering			$ (912)							$ (912)
Stock-based compensation	1,550						1,550
Issuance of shares related to reverse stock split, Shares				1,311
Other comprehensive income	1											1
Net loss	(13,480)										(13,480)
Stockholders Equity, Ending Balance at Dec. 31, 2018	$ 12,815			$ 45			$ 191,136				$ (178,366)	$ 0
Stockholders Equity, Ending Balance, Shares at Dec. 31, 2018				4,774,919