LONG-TERM DEBT - Narrative (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument
Outstanding balance	$ 268,125	$ 275,000
Term Loan | Term Loan due November 01, 2022
Debt Instrument
Outstanding balance	$ 268,100	$ 275,000
Term Loan | Term Loan due November 01, 2022 | Minimum
Debt Instrument
Interest coverage ratio	2.5
Term Loan | Term Loan due November 01, 2022 | Maximum
Debt Instrument
Net leverage ratio	4.5
Term Loan | Term Loan due November 01, 2022 | LIBOR | Minimum
Debt Instrument
Basis spread on variable rate (as a percent)	2.00%
Term Loan | Term Loan due November 01, 2022 | LIBOR | Maximum
Debt Instrument
Basis spread on variable rate (as a percent)	4.36%	3.38%
Term Loan | Term Loan due November 01, 2022 | Quarterly payments for first three years | Base Rate
Debt Instrument
Basis spread on variable rate (as a percent)	1.25%
Term Loan | Term Loan due November 01, 2022 | Quarterly payments in fourth year | Base Rate
Debt Instrument
Basis spread on variable rate (as a percent)	2.50%
Term Loan | Term Loan due November 01, 2022 | Quarterly payments in fifth year | Base Rate
Debt Instrument
Basis spread on variable rate (as a percent)	3.75%