UNAUDITED QUARTERLY FINANCIAL INFORMATION (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
UNAUDITED QUARTERLY FINANCIAL INFORMATION [Abstract]
Revenue	$ 67,401	$ 67,308	$ 61,865	$ 65,279	$ 72,568	$ 74,267	$ 68,080	$ 70,644	$ 261,853	$ 285,559	$ 306,102
Net (loss) income	$ 7,707	$ (1,490)	$ (6,771)	$ (10,929)	$ (18,628)	$ (471)	$ (3,138)	$ (6,068)	$ (11,484)	$ (28,304)	$ (3,350)
Basic [Abstract]
Net (loss) earnings per share (in dollars per share)	$ 0.32	$ (0.06)	$ (0.28)	$ (0.46)	$ (0.79)	$ (0.02)	$ (0.13)	$ (0.26)	$ (0.48)	$ (1.21)	$ (0.14)
Diluted [Abstract]
Net (loss) earnings per share (in dollars per share)	$ 0.31	$ (0.06)	$ (0.28)	$ (0.46)	$ (0.79)	$ (0.02)	$ (0.13)	$ (0.26)	$ (0.48)	$ (1.21)	$ (0.14)
Weighted average number of common shares outstanding:
Basic (in shares)	24,025,000	24,024,000	23,962,000	23,609,000	23,514,000	23,499,000	23,448,000	23,351,000	23,906,395	23,453,427	23,166,977
Diluted (in shares)	24,590,000	24,024,000	23,962,000	23,609,000	23,514,000	23,499,000	23,448,000	23,351,000	23,906,395	23,453,427	23,166,977