Condensed Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands	Total	Convertible Preferred Shares	Common Shares	Additional Paid-In Capital	Deficit	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2018		1,164,000	55,518,800
Beginning balance at Dec. 31, 2018	$ 200,234	$ 126,136	$ 879,405	$ 48,084	$ (805,221)	$ (48,170)
Accretion of accumulated dividends on Preferred Shares	0	$ 2,715			(2,715)
Stock-based compensation	1,665			1,665
Certain fair value adjustments to liability stock option awards	47			47
Issuance of common shares pursuant to the Sale Agreement	2,248
Issuance of common shares (in shares) pursuant to our Open Market Sales Agreement			614,401
Issuance of common shares pursuant to our Open Market Sales Agreement			$ 2,248
Issuance of common shares pursuant to exercise of options (in shares)			122,603
Issuance of common shares pursuant to exercise of options	288		$ 490	(202)
Unrealized gain on available-for-sale securities	(22)					(22)
Net loss	(23,251)				(23,251)
Ending balance (in shares) at Mar. 31, 2019		1,164,000	56,255,804
Ending balance at Mar. 31, 2019	181,209	$ 128,851	$ 882,143	49,594	(831,187)	(48,192)
Beginning balance (in shares) at Dec. 31, 2019		1,164,000	64,780,314
Beginning balance at Dec. 31, 2019	72,744	$ 137,285	$ 898,535	55,246	(970,093)	(48,229)
Accretion of accumulated dividends on Preferred Shares		$ (2,978)			2,978
Stock-based compensation	1,460			1,460
Certain fair value adjustments to liability stock option awards	180			180
Issuance of common shares pursuant to the Sale Agreement	12,315
Issuance of common shares (in shares) pursuant to our Open Market Sales Agreement			4,147,081
Issuance of common shares pursuant to our Open Market Sales Agreement			$ 12,315
Issuance of common shares pursuant to exercise of options (in shares)			34,000
Issuance of common shares pursuant to exercise of options	166		$ 249	(83)
Unrealized gain on available-for-sale securities	252					252
Net loss	(13,861)				(13,861)
Ending balance (in shares) at Mar. 31, 2020		1,164,000	68,961,395
Ending balance at Mar. 31, 2020	$ 73,256	$ 140,263	$ 911,099	$ 56,803	$ (986,932)	$ (47,977)