Statements of Changes in Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional paid-in Capital	Accumulated deficit	Total
Beginning Balances at Dec. 31, 2017	$ 559	$ 184,485	$ (160,604)	$ 24,440
Beginning Balances (in shares) at Dec. 31, 2017	55,888
Funds received from sale of DSPP units and shares	$ 94	13,687		13,781
Funds received from sale of DSPP units and shares (in shares)	9,466
Value of bonds converted to shares		176		176
Value of bonds converted to shares (in shares)	41
Bond interest paid in shares	$ 1	330		331
Bond interest paid in shares (in shares)	71
Funds received from option exercises	$ 3	16		19
Funds received from option exercises (in shares)	283
Value of options granted to employees, directors and others as non-cash compensation		1,855		1,855
Net income			(38,511)	(38,511)
Ending Balances at Dec. 31, 2018	$ 664	203,580	(199,115)	5,129
Ending Balances (in shares) at Dec. 31, 2018	66,405
Funds received from sale of DSPP units and shares	$ 565	13,667		14,232
Funds received from sale of DSPP units and shares (in shares)	56,430
Value of bonds converted to shares		3		3
Value of bonds converted to shares (in shares)	8
Bond interest paid in shares	$ 4	323		327
Bond interest paid in shares (in shares)	422
Funds received from option exercises	$ 7			7
Funds received from option exercises (in shares)	708
Value of options granted to employees, directors and others as non-cash compensation		319		319
Net income			(6,693)	(6,693)
Ending Balances at Dec. 31, 2019	$ 1,240	$ 217,892	$ (205,808)	$ 13,324
Ending Balances (in shares) at Dec. 31, 2019	123,973