Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common stock	Additional paid-in capital	Accumulated deficit	Total
Beginning balances at Dec. 31, 2013	$ 32	$ 448,981	$ (450,709)	$ (1,696)
Beginning balances, shares at Dec. 31, 2013	32,069
Share-based compensation expense	$ 0	705	0	705
Share-based compensation expense, shares	105
Sales of common stock and warrants	$ 9	16,105	0	16,114
Sales of common stock and warrants, shares	8,871
Exchange of warrants	$ 4	9,865	0	9,869
Exchange of warrants, shares	3,713
Net loss	$ 0	0	(18,120)	(18,120)
Ending balances at Dec. 31, 2014	$ 45	475,656	(468,829)	6,872
Ending balances, shares at Dec. 31, 2014	44,758
Share-based compensation expense	$ 0	1,011	0	1,011
Share-based compensation expense, shares	86
Sales of common stock and warrants	$ 1	3,205	0	3,206
Sales of common stock and warrants, shares	1,069
Exchange of warrants				0
Exercise of warrants and options	$ 1	3,299	0	3,300
Exercise of warrants and options, shares	1,510
Net loss	$ 0	0	(14,542)	(14,542)
Ending balances at Dec. 31, 2015	$ 47	483,171	(483,371)	(153)
Ending balances, shares at Dec. 31, 2015	47,423
Share-based compensation expense	$ 0	1,223	0	1,223
Share-based compensation expense, shares	87
Exercise of options	$ 0	7	0	7
Exercise of options, shares	4
Sales of common stock and warrants	$ 21	22,848	0	22,869
Sales of common stock and warrants, shares	20,579
Net loss	$ 0	0	(16,472)	(16,472)
Ending balances at Dec. 31, 2016	$ 68	$ 507,249	$ (499,843)	$ 7,474
Ending balances, shares at Dec. 31, 2016	68,093