QUARTERLY RESULTS OF OPERATIONS (unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
QUARTERLY RESULTS OF OPERATIONS (unaudited) [Abstract]
Revenues	$ 56,980	$ 55,576	$ 56,863	$ 58,978	$ 58,863	$ 58,553	$ 58,627	$ 58,409	$ 228,397	$ 234,452	$ 233,128
Income/(loss) from operations before taxes	(4,697)	(6,683)	(41,123)	8,960	10,559	9,151	9,998	6,752	(43,543)	36,460	25,933
Net income/(loss)	$ (2,623)	$ (4,042)	$ (25,109)	$ 5,649	$ 7,310	$ 5,763	$ 6,276	$ 5,011	$ (26,125)	$ 24,360	$ 16,484
Basic earnings per common share: [Abstract]
Basic net income/(loss) per share (in dollars per share)	$ (0.11)	$ (0.18)	$ (1.09)	$ 0.25	$ 0.32	$ 0.25	$ 0.27	$ 0.22	$ (1.14)	$ 1.06	$ 0.71
Diluted earnings per common share: [Abstract]
Diluted net income/(loss) per share (in dollars per share)	$ (0.11)	$ (0.18)	$ (1.09)	$ 0.24	$ 0.31	$ 0.25	$ 0.27	$ 0.22	$ (1.14)	$ 1.05	$ 0.70