LONG-TERM DEBT LIABILITIES - Debt Extinguishment and Net Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Interest Expense
Interest expense	$ 31,266	$ 33,799	$ 34,764
Amortization of deferred financing costs	2,333	2,585	2,863
Amortization of original issue discount of senior notes	(962)	312	340
Interest income and other investment income	(116)	(57)	(6)
Total net interest expense	32,521	36,639	37,961
Extinguishment of Debt [Line Items]
Gains (Losses) on Extinguishment of Debt	(4,135)	$ (10,858)	$ 0
New Credit Facility [Member] | New Revolver [Member]
Extinguishment of Debt [Line Items]
Deferred Financing Costs - 2017 Refinancing	200
New Credit Facility [Member] | New Term B Loan [Member]
Extinguishment of Debt [Line Items]
Deferred Financing Costs - 2017 Refinancing	15,000
Former Facility [Member] | Revolving Credit Facility [Member]
Extinguishment of Debt [Line Items]
Write-off of unamortized deferred financing costs	500
Deferred Financing Costs - 2017 Refinancing	400
Former Facility [Member] | Term Loan B [Member]
Extinguishment of Debt [Line Items]
Write-off of unamortized deferred financing costs	2,600
Former Facility [Member] | Modified Term B Loan [Member]
Extinguishment of Debt [Line Items]
Deferred Financing Costs - 2017 Refinancing	$ 3,200