LONG-TERM DEBT, LETTERS OF CREDIT AND DERIVATIVES - Subsequent Event Narrative (Details)		3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Jun. 17, 2020 USD ($)	Mar. 31, 2020	Jun. 30, 2020 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Jun. 30, 2021	Mar. 31, 2021	Aug. 30, 2019 USD ($)
Debt Instrument [Line Items]
Borrowing capacity								$ 275,000,000.0
LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		2.75%
Subsequent Event
Debt Instrument [Line Items]
Senior secured leverage ratio			3.50	3.25	2.75		2.50
Net leverage ratio						4.50	5.50
Debt service coverage ratio				1.00	1.25
Minimum consolidated EBITDA			$ 6,500,000	$ 18,500,000	$ 50,500,000
Subsequent Event | Minimum
Debt Instrument [Line Items]
Commitment fee percentage	0.35%
Subsequent Event | Maximum
Debt Instrument [Line Items]
Commitment fee percentage	0.55%
Subsequent Event | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate, floor	0.01
Subsequent Event | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	2.75%
Subsequent Event | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	4.25%
Credit Facility revolver
Debt Instrument [Line Items]
Borrowing capacity								$ 225,000,000.0
Credit Facility revolver | Subsequent Event
Debt Instrument [Line Items]
Borrowing capacity	$ 200,000,000