CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	At-the-Market Offering	Equity Offering	Common Stock	Common Stock At-the-Market Offering	Common Stock Equity Offering	Additional Paid-In Capital	Additional Paid-In Capital At-the-Market Offering	Additional Paid-In Capital Equity Offering	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance (in shares) at Dec. 31, 2021				4,881,851
Balance at Dec. 31, 2021	$ 16,026			$ 49			$ 402,283			$ (175)	$ (386,131)
Increase (decrease) in stockholders' equity
Stock-based compensation expense	1,012						1,012
Issuance of common stock for 401k match (in shares)				12,917
Issuance of common stock for 401(k) match	66			$ 0			66
Issuance of common stock for restricted stock units (in shares)				6,478
Taxes paid on employees' behalf related to vesting of stock awards	(14)						(14)
Effect of foreign currency translation and unrealized loss on investments	(45)									(45)
Net loss	(6,774)										(6,774)
Balance (in shares) at Jun. 30, 2022				4,901,246
Balance at Jun. 30, 2022	10,271			$ 49			403,347			(220)	(392,905)
Balance (in shares) at Mar. 31, 2022				4,893,403
Balance at Mar. 31, 2022	13,211			$ 49			402,817			(193)	(389,462)
Increase (decrease) in stockholders' equity
Stock-based compensation expense	489						489
Issuance of common stock for 401k match (in shares)				7,843
Issuance of common stock for 401(k) match	41						41
Effect of foreign currency translation and unrealized loss on investments	(27)									(27)
Net loss	(3,443)										(3,443)
Balance (in shares) at Jun. 30, 2022				4,901,246
Balance at Jun. 30, 2022	10,271			$ 49			403,347			(220)	(392,905)
Balance (in shares) at Dec. 31, 2022				4,944,202
Balance at Dec. 31, 2022	4,400			$ 49			404,277			(229)	(399,697)
Increase (decrease) in stockholders' equity
Stock-based compensation expense	805						805
Issuance of common stock for 401k match (in shares)				27,016
Issuance of common stock for 401(k) match	56			$ 1			55
Issuance of common stock and warrants in equity offering (net of issuance costs) (in shares)					94,665	1,006,710
Issuance of common stock and warrants in equity offering, net of issuance costs		$ 103	$ 2,717		$ 1	$ 10		$ 102	$ 2,707
Issuance of common stock for restricted stock units (in shares)				17,640
Taxes paid on employees' behalf related to vesting of stock awards	$ (41)						(41)
Issuance of common stock for director compensation (in shares)	10,030			10,030
Issuance of common stock for director compensation	$ 25						25
Effect of foreign currency translation and unrealized loss on investments	(15)									(15)
Net loss	(7,463)										(7,463)
Balance (in shares) at Jun. 30, 2023				6,100,263
Balance at Jun. 30, 2023	587			$ 61			407,930			(244)	(407,160)
Balance (in shares) at Mar. 31, 2023				5,078,557
Balance at Mar. 31, 2023	1,143			$ 51			404,803			(232)	(403,479)
Increase (decrease) in stockholders' equity
Stock-based compensation expense	381						381
Issuance of common stock for 401k match (in shares)				9,438
Issuance of common stock for 401(k) match	$ 26			$ 0			26
Issuance of common stock and warrants in equity offering (net of issuance costs) (in shares)						1,006,710
Issuance of common stock and warrants in equity offering, net of issuance costs			$ 2,717			$ 10			$ 2,707
Issuance of common stock for director compensation (in shares)	5,558			5,558
Issuance of common stock for director compensation	$ 13						13
Effect of foreign currency translation and unrealized loss on investments	(12)									(12)
Net loss	(3,681)										(3,681)
Balance (in shares) at Jun. 30, 2023				6,100,263
Balance at Jun. 30, 2023	$ 587			$ 61			$ 407,930			$ (244)	$ (407,160)