UNAUDITED QUARTERLY FINANCIAL INFORMATION (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	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, 2018	Dec. 31, 2017	Dec. 31, 2016
UNAUDITED QUARTERLY FINANCIAL INFORMATION [Abstract]
Revenue	$ 70,113	$ 70,078	$ 61,120	$ 61,889	$ 67,401	$ 67,308	$ 61,865	$ 65,279	$ 263,200	$ 261,853	$ 285,559
Net (loss) income	$ 5,033	$ (600)	$ (4,104)	$ (6,874)	$ 7,707	$ (1,490)	$ (6,771)	$ (10,929)	$ (6,545)	$ (11,484)	$ (28,304)
Basic [Abstract]
Net (loss) earnings per share (in dollars per share)	$ 0.21	$ (0.02)	$ (0.17)	$ (0.28)	$ 0.32	$ (0.06)	$ (0.28)	$ (0.46)	$ (0.27)	$ (0.48)	$ (1.21)
Diluted [Abstract]
Net (loss) earnings per share (in dollars per share)	$ 0.20	$ (0.02)	$ (0.17)	$ (0.28)	$ 0.31	$ (0.06)	$ (0.28)	$ (0.46)	$ (0.27)	$ (0.48)	$ (1.21)
Weighted average number of common shares outstanding [Abstract]
Basic (in shares)	24,533,000	24,533,000	24,486,000	24,138,000	24,025,000	24,024,000	23,962,000	23,609,000	24,423,479	23,906,395	23,453,427
Diluted (in shares)	24,562,000	24,533,000	24,486,000	24,138,000	24,590,000	24,024,000	23,962,000	23,609,000	24,423,479	23,906,395	23,453,427