LONG-TERM DEBT - Term Loan Credit Agreement Narrative (Details)		12 Months Ended
	Nov. 17, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Feb. 24, 2017 USD ($)	May 31, 2012 USD ($)
Debt Instrument [Line Items]
Long-term debt		$ 510,699,000	$ 557,233,000
Loss on debt extinguishment		280,000	799,000	$ 1,895,000
Amortization of debt issuance costs and discounts		200,000	200,000	200,000
Amended Credit Agreement
Debt Instrument [Line Items]
Interest paid, including capitalized interest, operating and investing activities		8,000,000	7,400,000	8,300,000
Long-term debt		1,900,000	1,900,000	$ 1,900,000
Loss on debt extinguishment			$ 700,000
Term Loan Credit Agreement
Debt Instrument [Line Items]
Long-term line of credit		185,700,000
Debt instrument, periodic payment, principal		$ 1,900,000
Term Loan Credit Agreement | Senior Secured Credit Facility
Debt Instrument [Line Items]
Long-term line of credit	$ 188,000,000				$ 189,500,000	$ 188,000,000.0
Line of credit facility accordion feature increase limit						$ 75,000,000
Debt instrument, covenant, secured leverage ratio						3.00
Percentage of tranche loan amount on equal quarterly installments	0.25%
London Interbank Offered Rate (LIBOR) | Term Loan Credit Agreement | Senior Secured Credit Facility
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	2.25%
Base Rate | Term Loan Credit Agreement | Senior Secured Credit Facility
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.25%