Consolidated Statements of Stockholders' Deficit - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit
Beginning balance at Dec. 31, 2017	$ 898	$ 2	$ 294,220	$ (293,324)
Beginning balance (in shares) at Dec. 31, 2017		15,889,171
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued for services	112		112
Common stock issued for outside services (in shares)		24,000
Warrants issued for services	86		86
Warrants issued in connection with A/R facility	64		64
Cashless warrant exercise (in shares)		241,975
Cash warrant exercise	150		150
Cash warrant exercise (in shares)		30,000
Stock compensation expense	2,056		2,056
Net loss	(14,212)			(14,212)
Ending balance at Dec. 31, 2018	$ (8,965)	$ 2	296,688	(305,655)
Ending balance (in shares) at Dec. 31, 2018	16,185,146	16,185,146
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Warrants issued for services	$ 43		43
Warrants issued in connection with 2024 notes	2,354		2,354
Cash warrant exercise	1,128		1,128
Cash warrant exercise (in shares)		232,461
Exercise of stock options	1,894		1,894
Exercise of stock options (in shares)		195,351
Stock compensation expense	5,210		5,210
Stock compensation expense (in shares)		3,207
Net loss	(25,659)			(25,659)
Ending balance at Dec. 31, 2019	$ (23,909)	$ 2	$ 307,403	$ (331,314)
Ending balance (in shares) at Dec. 31, 2019	16,616,165	16,616,165