LONG-TERM DEBT - Narrative (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2017 USD ($)	Nov. 30, 2017 USD ($)
Debt Instrument [Line Items]
Undivided interest (as a percent)									75.00%
Loss on debt extinguishment	$ 0	$ 0	$ 3,149,000	$ 0
Loans Payable | Term Loan A
Debt Instrument [Line Items]
Maximum borrowing capacity									$ 100,000,000
Principal	100,000,000		100,000,000
Repayment on line of credit			26,000,000
Accelerated repayment			15,000,000
Loans Payable | Term Loan B
Debt Instrument [Line Items]
Maximum borrowing capacity									400,000,000
Principal	400,000,000		400,000,000
Senior Notes | Senior Secured Second Lien Notes due 2025
Debt Instrument [Line Items]
Principal	$ 300,000,000		$ 300,000,000						$ 300,000,000
Stated interest rate (as a percent)	11.00%		11.00%						11.00%
Debt repurchased	$ 21,000,000		$ 21,000,000
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity									$ 300,000,000
First lien gross leverage ratio, maximum	2.25		2.25
First lien gross leverage ratio, actual	1.29		1.29
Total net leverage ratio, maximum	3.25		3.25
Total net leverage ratio, actual	1.63		1.63
Fixed charge coverage ratio, minimum	1.00		1.00
Fixed charge coverage ratio	2.17		2.17
Outstanding borrowings	$ 0		$ 0					$ 0
Letters of credit outstanding	54,065,000		54,065,000					27,426,000
Borrowings and issuance of letters of credit remaining capacity	$ 245,935,000		$ 245,935,000					$ 272,574,000
Revolving Credit Facility | Line of Credit | Scenario, Forecast
Debt Instrument [Line Items]
First lien gross leverage ratio, maximum						1.75	2.00
Total net leverage ratio, maximum						2.75	3.00
Fixed charge coverage ratio, minimum					1.10	1.05