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, 2017	$ 79	$ 528,873	$ (524,086)	$ 4,866
Beginning balances, shares at Dec. 31, 2017	78,597
Adoption of New Accounting Pronouncement, Revenue from Contracts with Customers	$ 0	0	5,220	5,220
Share-based compensation expense	$ 0	332	0	332
Share-based compensation expense, shares	16
Net loss	$ 0	0	(7,132)	(7,132)
Ending balances at Mar. 31, 2018	$ 79	529,205	(525,998)	3,286
Ending balances, shares at Mar. 31, 2018	78,613
Beginning balances at Dec. 31, 2018	$ 100	550,133	(546,116)	4,117
Beginning balances, shares at Dec. 31, 2018	100,105
Share-based compensation expense	$ 0	351	0	351
Share-based compensation expense, shares	0
Sales of common stock	$ 2	1,166	0	1,168
Sales of common stock, shares	2,000
Net loss	$ 0	0	(8,068)	(8,068)
Ending balances at Mar. 31, 2019	$ 102	$ 551,650	$ (554,184)	$ (2,432)
Ending balances, shares at Mar. 31, 2019	102,105