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)
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					(18,243)
Net loss and comprehensive loss					(18,243)
Balance (in shares) at Sep. 30, 2018		24,453,358
Balance at Sep. 30, 2018		$ 245	381,824	(461,978)	(79,909)
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
Issuance of shares pursuant to ATM offerings (in shares)		1,159,718
Issuance of shares pursuant to ATM offerings		$ 12	14,570		14,582
Net loss and comprehensive loss				(6,032)	(6,032)
Net loss and comprehensive loss				(6,032)	(6,032)
Balance (in shares) at Jun. 30, 2018		24,425,296
Balance at Jun. 30, 2018		$ 244	381,556	(455,738)	(73,938)
Issuance of shares pursuant to bond conversion (in shares)		21,557
Issuance of shares pursuant to bond conversion		$ 1	145		146
Stock-based compensation expense (in shares)		6,505
Stock-based compensation expense			123		123
Net loss and comprehensive loss				(6,240)	(6,240)
Net loss and comprehensive loss				(6,240)	(6,240)
Balance (in shares) at Sep. 30, 2018		24,453,358
Balance at Sep. 30, 2018		$ 245	381,824	(461,978)	(79,909)
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
Issuance of shares pursuant to ATM offerings (in shares)		782,814
Issuance of shares pursuant to ATM offerings		$ 7	7,884		7,891
Reclassification of warrant liability to additional paid-in capital (1)	[1]		2,896	(2,031)	865
Net loss and comprehensive loss				(7,260)	(7,260)
Net loss and comprehensive loss				(7,260)	(7,260)
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)					845,081
Net loss and comprehensive loss					$ (22,180)
Net loss and comprehensive loss					(22,180)
Balance (in shares) at Sep. 30, 2019		26,996,060
Balance at Sep. 30, 2019		$ 270	407,330	(494,243)	(86,643)
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
Issuance of shares pursuant to ATM offerings (in shares)		655,733
Issuance of shares pursuant to ATM offerings		$ 7	6,745		6,752
Reclassification of warrant liability to additional paid-in capital (1)			24	(24)
Net loss and comprehensive loss				(7,476)	(7,476)
Net loss and comprehensive loss				(7,476)	(7,476)
Balance (in shares) at Jun. 30, 2019		26,942,085
Balance at Jun. 30, 2019		$ 269	406,762	(486,799)	(79,768)
Issuance of shares pursuant to bond conversion (in shares)		23,164
Issuance of shares pursuant to bond conversion		$ 1	156		157
Stock-based compensation expense (in shares)		8,907
Stock-based compensation expense			165		165
Issuance of shares pursuant to ATM offerings (in shares)		21,904
Issuance of shares pursuant to ATM offerings			247		247
Net loss and comprehensive loss				(7,444)	(7,444)
Net loss and comprehensive loss				(7,444)	(7,444)
Balance (in shares) at Sep. 30, 2019		26,996,060
Balance at Sep. 30, 2019		$ 270	$ 407,330	$ (494,243)	$ (86,643)

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