CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Common Stock Registered direct purchase agreement	Common Stock	Additional Paid-in Capital Registered direct purchase agreement	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive income (loss)	LPC Program	Registered direct purchase agreement	Total
Increase (Decrease) in Stockholders' Equity
Cumulative adjustment related to change in accounting principle | Cumulative Effect Adjustment | ASU 2014-09 Revenue from Contracts with Customers					$ (89)	$ 40			$ (49)
Adjusted balance at beginning of period		$ 919		$ 516,284	(509,171)				8,032
Balance (Previously Reported) at Dec. 31, 2017		$ 919		516,284	(509,082)	$ (40)			8,081
Balance (in shares) (Previously Reported) at Dec. 31, 2017		91,929,709
Balance (in shares) at Dec. 31, 2017		91,929,709
Increase (Decrease) in Stockholders' Equity
Stock compensation accrued				45					45
Net loss					(735)				(735)
Balance at Mar. 31, 2018		$ 919		516,329	(509,906)				7,342
Balance (in shares) at Mar. 31, 2018		91,929,709
Increase (Decrease) in Stockholders' Equity
Stock compensation accrued and shares issued for vested stock awards		$ 4		267					271
Stock compensation accrued and shares issued for vested stock awards (in shares)		537,279
Registered direct purchase agreement, net	$ 32		$ 1,202					$ 1,234
Registered direct purchase agreement, net (in shares)	3,153,808
Deemed dividend on warrants				8	(8)
Net loss					(1,210)				(1,210)
Balance at Dec. 31, 2018		$ 955		517,806	(511,124)				7,637
Balance (in shares) at Dec. 31, 2018		95,620,796
Increase (Decrease) in Stockholders' Equity
Stock compensation accrued				337					337
Modification of previously awarded KELTIP Units				583					583
Shares issued under the at-the-market offering agreement, net		$ 1		11					12
Shares issued under the at-the-market offering agreement, net (in shares)		33,995
Shares issued under the Lincoln Park commitment purchase agreement, net		$ 12		313					325
Shares issued under the Lincoln Park commitment purchase agreement, net (in shares)		1,213,642
Registered direct purchase agreement, net (in shares)							1,213,642
Net loss					(2,351)				(2,351)
Balance at Mar. 31, 2019		$ 968		$ 519,050	$ (513,475)				$ 6,543
Balance (in shares) at Mar. 31, 2019		96,868,433