LOSS PER SHARE CALCULATION - Calculation of Earning Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												6 Months Ended		9 Months Ended		12 Months Ended			36 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2018	Mar. 31, 2017	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2019
Numerator for basic and diluted loss per share
Net loss	$ (10,541)	$ (4,510)	$ (10,657)	$ (6,320)	$ (1,696)	$ (3,223)	$ (4,194)	$ (2,171)	$ (2,938)	$ (925)	$ (232)	$ (3,370)	$ (6,365)	$ (3,602)	$ (9,588)	$ (4,527)	$ (32,028)	$ (11,284)	$ (7,465)	$ (50,800)
Preferred dividends	0	(334)	0	(334)	0	(334)	0	(334)	0	(334)	0	(334)	(334)	(334)	(668)	(668)	(668)	(668)	(668)
Net loss applicable to common shares	$ (10,541)	$ (4,844)	$ (10,657)	$ (6,654)	$ (1,696)	$ (3,557)	$ (4,194)	$ (2,505)	$ (2,938)	$ (1,259)	$ (232)	$ (3,704)	$ (6,699)	$ (3,936)	$ (10,256)	$ (5,195)	$ (32,696)	$ (11,952)	$ (8,133)
Denominator for basic loss per share - weighted average shares outstanding (in shares)	60,065,978	60,065,053	60,059,936	60,053,912	54,064,750	53,637,085	52,150,106	47,573,364	40,331,993	40,327,697	40,308,934	38,488,005	49,861,735	39,398,469	51,101,813	39,703,690	60,061,243	51,840,518	39,860,335
Effect of dilutive potential common shares (in shares)																	0	0	0
Denominator for diluted loss per share (in shares)	60,065,978	60,065,053	60,059,936	60,053,912	54,064,750	53,637,085	52,150,106	47,573,364	40,331,993	40,327,697	40,308,934	38,488,005	49,861,735	39,398,469	51,101,813	39,703,690	60,061,243	51,840,518	39,860,335
Basic loss per share (in USD per share)	$ (0.18)	$ (0.08)	$ (0.18)	$ (0.11)	$ (0.03)	$ (0.07)	$ (0.08)	$ (0.05)	$ (0.07)	$ (0.03)	$ (0.01)	$ (0.10)	$ (0.13)	$ (0.10)	$ (0.20)	$ (0.13)	$ (0.54)	$ (0.23)	$ (0.20)
Diluted loss per share (in USD per share)	$ (0.18)	$ (0.08)	$ (0.18)	$ (0.11)	$ (0.03)	$ (0.07)	$ (0.08)	$ (0.05)	$ (0.07)	$ (0.03)	$ (0.01)	$ (0.10)	$ (0.13)	$ (0.10)	$ (0.20)	$ (0.13)	$ (0.54)	$ (0.23)	$ (0.20)