LOSS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Earnings Per Share [Abstract]
Common stock, par value (in dollars per share)	$ 0.0001				$ 0.0001		$ 0.0001
Numerator:
Loss from continuing operations	$ (14,166)		$ (15,124)		$ (24,448)	$ (28,111)
Loss from discontinued operations, net of income taxes	(1,500)		(15)		(1,500)	(45)
Net loss	(15,666)	$ (10,282)	(15,139)	$ (13,017)	(25,948)	(28,156)
Accrued dividends on preferred stock	(3,068)		(2,756)		(6,025)	(5,413)
Loss attributable to common stockholders	(18,734)		(17,895)		(31,973)	(33,569)
Income effect of 2017 Warrants	0		0		(4,784)	(375)
Loss attributable to common stockholders, diluted	$ (18,734)		$ (17,895)		$ (36,757)	$ (33,944)
Denominator:
Weighted average number of common shares outstanding, basic (in shares)	128,779		128,038		128,446	127,906
Dilutive effect of 2017 Warrants (in shares)	0		0		2,053	2,252
Weighted average number of common shares outstanding, diluted (in shares)	128,779		128,038		130,499	130,158
Basic loss per share:
Loss from continuing operations (in dollars per share)	$ (0.13)		$ (0.14)		$ (0.24)	$ (0.26)
Loss from discontinued operations (in dollars per share)	(0.01)		0.00		(0.01)	0.00
Basic loss per share (in dollars per share)	(0.14)		(0.14)		(0.25)	(0.26)
Diluted loss per share:
Loss from continuing operations (in dollars per share)	(0.13)		(0.14)		(0.27)	(0.26)
Loss from discontinued operations (in dollars per share)	(0.01)		0.00		(0.01)	0.00
Diluted loss per share (in dollars per share)	(0.14)		$ (0.14)		(0.28)	$ (0.26)
Series A Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock series, par value (in dollars per share)	0.0001				0.0001		0.0001
Series C Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock series, par value (in dollars per share)	$ 0.0001				$ 0.0001		$ 0.0001