LONG-TERM DEBT - Narrative (Details)		3 Months Ended		9 Months Ended		12 Months Ended
	Mar. 28, 2019 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) Financing_Arrangement	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Mar. 31, 2020	Nov. 30, 2017 USD ($)
Debt Instrument [Line Items]
Undivided interest								75.00%
Loss on debt extinguishment		$ 801,000	$ 0	$ 25,444,000	$ 3,149,000
Number of asset-backed financing arrangements | Financing_Arrangement				2
Collateral amount		7,591,000		$ 7,591,000
Loans Payable | Term Loan A
Debt Instrument [Line Items]
Maximum borrowing capacity		100,000,000		100,000,000				$ 100,000,000
Amendment to basis points	0.50%
Repayment on line of credit					26,000,000
Principal		100,000,000		100,000,000
Accelerated repayment					$ 15,000,000
Loans Payable | Term Loan B
Debt Instrument [Line Items]
Maximum borrowing capacity		275,000,000		275,000,000				400,000,000
Amendment to basis points	1.50%
Repayment on line of credit				$ 110,000,000
Repayment, percent of excess cash flow						75.00%
Repayment, decrease to percent of excess cash flow				25.00%
Repayment on line of credit if covenant applicable		7,000,000		$ 7,000,000
Principal		275,000,000		275,000,000
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		11.00%	11.00%	11.00%	11.00%			11.00%
Debt repurchased		$ 35,000,000	$ 21,000,000	$ 35,000,000	$ 21,000,000
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 400,000,000							$ 300,000,000
First lien gross leverage ratio, maximum		2.00		2.00
First lien gross leverage ratio, actual		1.15		1.15
Total net leverage ratio, maximum		3.00		3.00
Total net leverage ratio, actual		1.78		1.78
Fixed charge coverage ratio, minimum		1.10		1.10
Fixed charge coverage ratio		1.46		1.46
Outstanding borrowings		$ 0		$ 0		$ 0
Letters of credit outstanding		73,732,000		73,732,000		54,065,000
Borrowings and issuance of letters of credit remaining capacity		$ 326,268,000		$ 326,268,000		$ 245,935,000
Revolving Credit Facility | Line of Credit | Scenario, Forecast
Debt Instrument [Line Items]
First lien gross leverage ratio, maximum							1.75
Total net leverage ratio, maximum							2.75
Minimum | Loans Payable | Term Loan B
Debt Instrument [Line Items]
Repayment, percent of excess cash flow				0.00%
Maximum | Loans Payable | Term Loan B
Debt Instrument [Line Items]
Repayment, percent of excess cash flow				75.00%