Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands		Total	Preferred Stock	Preferred Stock	Preferred Stock Preferred Stock	Common Stock		Additional Paid-in Capital	Additional Paid-in Capital Preferred Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance at the beginning of the period (in shares) at Dec. 31, 2019				0		2,486,000	[1]
Balance at the beginning of the period at Dec. 31, 2019		$ 3,996		$ 0		$ 0		$ 128,873		$ (3)	$ (124,874)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock option and stock purchase plans (in shares)	[1]					5,000
Issuance of common stock under employee stock option and stock purchase plans		0
Offering costs on issuance of common stock and warrants		(474)						(474)
Warrant liability		(1,636)						(1,636)
Issuance of common stock and warrants (in shares)	[1]					688,000
Issuance of common stock and warrants		2,749						2,749
Conversion of notes to preferred stock (in shares)					2,709,000
Conversion of notes to preferred stock			$ 1,769						$ 1,769
Stock-based compensation		20						20
Net loss		(541)									(541)
Balance at the end of the period (in shares) at Mar. 31, 2020				2,709,000		3,179,000	[1]
Balance at the end of the period at Mar. 31, 2020		5,883		$ 0		$ 0		131,301		(3)	(125,415)
Balance at the beginning of the period (in shares) at Dec. 31, 2019				0		2,486,000	[1]
Balance at the beginning of the period at Dec. 31, 2019		3,996		$ 0		$ 0		128,873		(3)	(124,874)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss		(6,046)
Balance at the end of the period (in shares) at Sep. 30, 2020				2,597,000		3,428,000	[1],[2]
Balance at the end of the period at Sep. 30, 2020		2,139		$ 0		$ 0		133,062		(3)	(130,920)
Balance at the beginning of the period (in shares) at Mar. 31, 2020				2,709,000		3,179,000	[1]
Balance at the beginning of the period at Mar. 31, 2020		5,883		$ 0		$ 0		131,301		(3)	(125,415)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock option and stock purchase plans (in shares)	[1]					0
Issuance of common stock under employee stock option and stock purchase plans		30						30
Issuance of common stock upon the exercise of warrants (in shares)	[1]					15,000
Issuance of common stock upon the exercise of warrants		103						103
Common stock withheld in lieu of income tax withholding on vesting of restricted stock units		(3)						(3)
Conversion of notes to preferred stock (in shares)				112,000		22,000	[1]
Stock-based compensation		41						41
Net loss		(4,340)									(4,340)
Balance at the end of the period (in shares) at Jun. 30, 2020				2,597,000		3,216,000	[1]
Balance at the end of the period at Jun. 30, 2020		1,714		$ 0		$ 0		131,472		(3)	(129,755)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock option and stock purchase plans (in shares)	[1]					30,000
Issuance of common stock under employee stock option and stock purchase plans		0						0
Issuance of common stock upon the exercise of warrants (in shares)	[1]					182,000
Issuance of common stock upon the exercise of warrants		1,555						1,555
Stock-based compensation		35						35
Net loss		(1,165)									(1,165)
Balance at the end of the period (in shares) at Sep. 30, 2020				2,597,000		3,428,000	[1],[2]
Balance at the end of the period at Sep. 30, 2020		2,139		$ 0		$ 0		133,062		(3)	(130,920)
Balance at the beginning of the period (in shares) at Dec. 31, 2020				2,597,000		3,525,000
Balance at the beginning of the period at Dec. 31, 2020		4,255		$ 0		$ 0		135,113		(3)	(130,855)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock option and stock purchase plans (in shares)						1,000
Issuance of common stock under employee stock option and stock purchase plans		0
Issuance of common stock upon the exercise of warrants (in shares)						156,000
Issuance of common stock upon the exercise of warrants		527						527
Common stock withheld in lieu of income tax withholding on vesting of restricted stock units (in shares)						0
Common stock withheld in lieu of income tax withholding on vesting of restricted stock units		(2)						(2)
Stock-based compensation		140						140
Net loss		(1,642)									(1,642)
Balance at the end of the period (in shares) at Mar. 31, 2021				2,597,000		3,682,000
Balance at the end of the period at Mar. 31, 2021		3,278		$ 0		$ 0		135,778		(3)	(132,497)
Balance at the beginning of the period (in shares) at Dec. 31, 2020				2,597,000		3,525,000
Balance at the beginning of the period at Dec. 31, 2020		$ 4,255		$ 0		$ 0		135,113		(3)	(130,855)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon the exercise of warrants (in shares)		156,446
Net loss		$ (5,255)
Balance at the end of the period (in shares) at Sep. 30, 2021				876,000		5,087,000
Balance at the end of the period at Sep. 30, 2021		4,502		$ 0		$ 0		140,615		(3)	(136,110)
Balance at the beginning of the period (in shares) at Mar. 31, 2021				2,597,000		3,682,000
Balance at the beginning of the period at Mar. 31, 2021		3,278		$ 0		$ 0		135,778		(3)	(132,497)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock option and stock purchase plans (in shares)						69,000
Issuance of common stock under employee stock option and stock purchase plans		59						59
Offering costs on issuance of common stock and warrants		(469)						(469)
Issuance of common stock and warrants (in shares)						990,000
Issuance of common stock and warrants		5,000						5,000
Conversion of notes to preferred stock (in shares)				1,721,000		344,000
Stock-based compensation		208						208
Net loss		(2,473)									(2,473)
Balance at the end of the period (in shares) at Jun. 30, 2021				876,000		5,085,000
Balance at the end of the period at Jun. 30, 2021		5,603		$ 0		$ 0		140,576		(3)	(134,970)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock option and stock purchase plans (in shares)						2,000
Issuance of common stock under employee stock option and stock purchase plans		0
Offering costs on issuance of common stock and warrants		(1)						(1)
Common stock withheld in lieu of income tax withholding on vesting of restricted stock units		1						1
Stock-based compensation		39						39
Net loss		(1,140)									(1,140)
Balance at the end of the period (in shares) at Sep. 30, 2021				876,000		5,087,000
Balance at the end of the period at Sep. 30, 2021		$ 4,502		$ 0		$ 0		$ 140,615		$ (3)	$ (136,110)

[1] Shares outstanding for prior periods have been restated for the 1-for-5 reverse stock split effective June 11, 2020.

[2] * Shares outstanding for the nine months ended September 30, 2020 have been restated for the 1-for-5 reverse stock split effective June 11, 2020.