Consolidated Statements of Shareholders' Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Common stock	Additional paid-in capital	Accumulated deficit	Total
Beginning balances at Dec. 31, 2017	$ 79	$ 528,873	$ (518,866)	$ 10,086
Beginning balances, shares at Dec. 31, 2017	78,597
Share-based compensation expense	$ 0	1,061	0	$ 1,061
Share-based compensation expense, shares	108
Exercise of options, shares				0
Sales of common stock	$ 21	20,199	0	$ 20,220
Sales of common stock, shares	21,400
Net loss	$ 0	0	(27,250)	(27,250)
Ending balances at Dec. 31, 2018	$ 100	550,133	(546,116)	4,117
Ending balances, shares at Dec. 31, 2018	100,105
Share-based compensation expense	$ 1	1,613	0	$ 1,614
Share-based compensation expense, shares	822
Exercise of options, shares				0
Sales of common stock	$ 25	16,750	0	$ 16,775
Sales of common stock, shares	24,876
Net loss	$ 0	0	(26,483)	(26,483)
Ending balances at Dec. 31, 2019	$ 126	$ 568,496	$ (572,599)	$ (3,977)
Ending balances, shares at Dec. 31, 2019	125,803