FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets:
Cash and cash equivalents	$ 22,690	$ 35,409
Restricted cash	446	714
Interest rate swaps	8,570	10,748
Total assets	31,706	46,871
Liabilities:
Interest rate swaps	1,093	392
Total liabilities	1,093	392
Debt outstanding, fair value	1,130,000	1,305,000
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	22,690	35,409
Restricted cash	446	714
Interest rate swaps	0	0
Total assets	23,136	36,123
Liabilities:
Interest rate swaps	0	0
Total liabilities	0	0
Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents	0	0
Restricted cash	0	0
Interest rate swaps	8,570	10,748
Total assets	8,570	10,748
Liabilities:
Interest rate swaps	1,093	392
Total liabilities	1,093	392
Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Restricted cash	0	0
Interest rate swaps	0	0
Total assets	0	0
Liabilities:
Interest rate swaps	0	0
Total liabilities	$ 0	$ 0