Consolidated Statements of Shareholders' Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Common stock	Additional paid-in capital	Subscriptions receivable	Accumulated deficit	Total
Beginning balances at Dec. 31, 2018	$ 100	$ 550,133	$ 0	$ (546,116)	$ 4,117
Beginning balances, shares at Dec. 31, 2018	100,105
Share-based compensation expense	$ 1	1,613	0	0	$ 1,614
Share-based compensation expense, shares	822
Exercise of options, shares					0
Sales of common stock	$ 25	16,750	0	0	$ 16,775
Sales of common stock, shares	24,876
Net loss	$ 0	0	0	(26,483)	(26,483)
Ending balances at Dec. 31, 2019	$ 126	568,496	0	(572,599)	(3,977)
Ending balances, shares at Dec. 31, 2019	125,803
Share-based compensation expense	$ 0	1,252	0	0	1,252
Share-based compensation expense, shares	201
Exercise of options	$ 1	999	0	0	$ 1,000
Exercise of options, shares	693				693
Sales of common stock	$ 26	30,477	(6,135)	0	$ 24,368
Sales of common stock, shares	26,229
Net loss	$ 0	0	0	(13,634)	(13,634)
Ending balances at Dec. 31, 2020	$ 153	$ 601,224	$ (6,135)	$ (586,233)	$ 9,009
Ending balances, shares at Dec. 31, 2020	152,926