Statement of Changes in Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Beginning balance at Dec. 31, 2018	$ 71,042	$ 177	$ 291,908	$ (221,043)
Beginning balance, shares at Dec. 31, 2018		17,744
Share-based awards and options exercises	1,407	$ 5	1,402
Share-based awards and options exercises, shares		483
Share-based compensation expense	501		501
Net loss	(7,529)			(7,529)
Ending balance at Mar. 31, 2019	65,421	$ 182	293,811	(228,572)
Ending balance, shares at Mar. 31, 2019		18,227
Beginning balance at Dec. 31, 2019	47,852	$ 186	297,753	(250,087)
Beginning balance, shares at Dec. 31, 2019		18,645
Share-based awards and options exercises	76	$ 1	75
Share-based awards and options exercises, shares		81
Share-based compensation expense	1,196		1,196
Net loss	(12,613)			(12,613)
Ending balance at Mar. 31, 2020	$ 36,511	$ 187	$ 299,024	$ (262,700)
Ending balance, shares at Mar. 31, 2020		18,726