Condensed Consolidated Statements of Stockholders' Deficit (Unaudited) - USD ($) $ in Thousands		Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Dec. 31, 2017		22,987,434
Balance at Dec. 31, 2017		$ 230	$ 364,806	$ (443,735)	$ (78,699)
Issuance of shares pursuant to bond conversion (in shares)		215,852
Issuance of shares pursuant to bond conversion		$ 2	1,669		1,671
Stock-based compensation expense (in shares)		13,249
Stock-based compensation expense			105		105
Net loss and comprehensive loss				(5,971)	(5,971)
Balance (in shares) at Mar. 31, 2018		23,216,535
Balance at Mar. 31, 2018		$ 232	366,580	(449,706)	(82,894)
Balance (in shares) at Dec. 31, 2017		22,987,434
Balance at Dec. 31, 2017		$ 230	364,806	(443,735)	(78,699)
Net loss and comprehensive loss					(12,003)
Balance (in shares) at Jun. 30, 2018		24,425,296
Balance at Jun. 30, 2018		$ 244	381,556	(455,738)	(73,938)
Balance (in shares) at Mar. 31, 2018		23,216,535
Balance at Mar. 31, 2018		$ 232	366,580	(449,706)	(82,894)
Issuance of shares pursuant to bond conversion (in shares)		42,071
Issuance of shares pursuant to bond conversion			284		284
Stock-based compensation expense (in shares)		6,972
Stock-based compensation expense			122		122
Net loss and comprehensive loss				(6,032)	(6,032)
Issuance of shares pursuant to ATM offering (in shares)		1,159,718
Issuance of shares pursuant to ATM offering		$ 12	14,570		14,582
Balance (in shares) at Jun. 30, 2018		24,425,296
Balance at Jun. 30, 2018		$ 244	381,556	(455,738)	(73,938)
Balance (in shares) at Dec. 31, 2018		24,654,911
Balance at Dec. 31, 2018		$ 247	383,521	(470,008)	(86,240)
Issuance of shares pursuant to bond conversion (in shares)		485,020
Issuance of shares pursuant to bond conversion		$ 5	3,199		3,204
Stock-based compensation expense (in shares)		17,307
Stock-based compensation expense			122		122
Net loss and comprehensive loss				(7,260)	(7,260)
Issuance of shares pursuant to ATM offering (in shares)		782,814
Issuance of shares pursuant to ATM offering		$ 7	7,884		7,891
Reclassification of warrant liability to additional paid-in capital(1)	[1]		2,896	(2,031)	865
Balance (in shares) at Mar. 31, 2019		25,940,052
Balance at Mar. 31, 2019		$ 259	397,622	(479,299)	(81,418)
Balance (in shares) at Dec. 31, 2018		24,654,911
Balance at Dec. 31, 2018		$ 247	383,521	(470,008)	$ (86,240)
Issuance of shares pursuant to bond conversion (in shares)					821,917
Net loss and comprehensive loss					$ (14,736)
Balance (in shares) at Jun. 30, 2019		26,942,085
Balance at Jun. 30, 2019		$ 269	406,762	(486,799)	(79,768)
Balance (in shares) at Mar. 31, 2019		25,940,052
Balance at Mar. 31, 2019		$ 259	397,622	(479,299)	(81,418)
Issuance of shares pursuant to bond conversion (in shares)		336,897
Issuance of shares pursuant to bond conversion		$ 3	2,248		2,251
Stock-based compensation expense (in shares)		9,403
Stock-based compensation expense			123		123
Net loss and comprehensive loss				(7,476)	(7,476)
Issuance of shares pursuant to ATM offering (in shares)		655,733
Issuance of shares pursuant to ATM offering		$ 7	6,745		6,752
Reclassification of warrant liability to additional paid-in capital(1)			24	(24)
Balance (in shares) at Jun. 30, 2019		26,942,085
Balance at Jun. 30, 2019		$ 269	$ 406,762	$ (486,799)	$ (79,768)

[1] A cumulative effect adjustment of $2,031 thousand was recognized as of January 1, 2019, upon adoption of ASU 2017-11