LONG TERM DEBT AND CAPITAL LEASES - Components of Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Interest expense on long-term debt and capital leases	$ 22,060	$ 34,741	$ 35,868
Amortization of debt issuance costs and discounts on long-term debt	2,692	3,881	3,977
Letter of credit fees	703	593	637
Less: capitalized interest	(295)	(273)	(62)
Total interest expense	$ 25,160	$ 38,942	$ 40,420