CREDIT FACILITY (Details) $ in Thousands					3 Months Ended				9 Months Ended
	Jun. 18, 2021 USD ($)	Feb. 12, 2021 USD ($)	Apr. 08, 2020 USD ($)	Sep. 04, 2019 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Mar. 31, 2020	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Jan. 23, 2020 USD ($)
Line of Credit Facility [Line Items]
Long-term debt, gross					$ 192,631				$ 192,631		$ 246,999
Payment of debt issuance cost				$ 6,100					2,133	$ 1,148
Amortization of debt issuance costs									876	783
Consolidated EBITDA, maximum amount									$ 46,900
Consolidated EBITDA, percentage									1.000
Debt instrument, leverage ratio					7.4				7.4
Annual excess cash flow, percentage									0.50
Net cash proceeds of certain asset sales or casualty events, percentage									1
Net cash proceeds of debt, percentage									1
Prepayment premium on early repayment of term loan									$ 1,563	0
Loss on extinguishment of debt	$ 5,000				$ 0		$ 0		$ 5,015	$ 0
Long-term debt, irrevocable letter of credit threshold												$ 500
Long-term debt, irrevocable letter of credit, extension period									1 year
IPO
Line of Credit Facility [Line Items]
Prepayment premium on early repayment of term loan	131,500
Unamortized Deferred Financing Costs
Line of Credit Facility [Line Items]
Loss on extinguishment of debt	3,400
Prepayment Premiums
Line of Credit Facility [Line Items]
Loss on extinguishment of debt	$ 1,600
Minimum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate									0.375%
Maximum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate									0.50%
London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate									1.00%
Secured Debt
Line of Credit Facility [Line Items]
Long-term debt, gross					192,600				$ 192,600		222,200
Amortization of debt issuance costs				$ 5,200
Debt issuance costs, amortization period				84 months
Long-term debt, weighted average interest rate, over time									6.30%	6.60%
2020 Incremental Term Loan
Line of Credit Facility [Line Items]
Long-term debt, gross					24,800				$ 24,800
Term Loans
Line of Credit Facility [Line Items]
Amortization of debt issuance costs					200		$ 200		700	$ 600
Debt instrument, aggregate principal amount, payment, percentage								0.0025
Unamortized debt issuance expense					3,100				$ 3,100		5,200
Term Loans | Secured Debt
Line of Credit Facility [Line Items]
Debt instrument, face amount				$ 225,000
Debt instrument, term				7 years
2020 Incremental Term Loan
Line of Credit Facility [Line Items]
Long-term debt, weighted average interest rate, over time									10.00%
2020 Incremental Term Loan | Secured Debt
Line of Credit Facility [Line Items]
Debt instrument, face amount			$ 25,000
Debt issuance costs, amortization period			77 months
Debt issuance costs, gross			$ 1,100
Debt instrument, aggregate principal amount, payment, percentage						0.0025	0.0025
2021 Incremental Term Loan
Line of Credit Facility [Line Items]
Long-term debt, weighted average interest rate, over time									7.00%
2021 Incremental Term Loan | Secured Debt
Line of Credit Facility [Line Items]
Debt instrument, face amount		$ 78,000
Debt issuance costs, amortization period		67 months
Debt issuance costs, gross		$ 2,400
Debt instrument, quarterly payment amount						$ 800
Credit Agreement | London Interbank Offered Rate (LIBOR) | Minimum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate									5.25%
Credit Agreement | London Interbank Offered Rate (LIBOR) | Maximum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate									4.75%
Credit Agreement | Base Rate | Minimum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate									4.25%
Credit Agreement | Base Rate | Maximum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate									3.75%
Credit Agreement | Eurodollar | Minimum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate									1.00%
Credit Agreement | Eurodollar | Maximum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate									0.75%
Revolving Credit Facility
Line of Credit Facility [Line Items]
Long-term debt, gross					39,500				$ 39,500		39,500
Amortization of debt issuance costs					50		$ 50		100	$ 100
Unamortized debt issuance expense					500				$ 500		$ 700
Long-term debt, weighted average interest rate, over time									2.75%	2.75%
Revolving Credit Facility | Line of Credit
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity				$ 40,000
Debt instrument, term				5 years
Amortization of debt issuance costs				$ 900
Debt issuance costs, amortization period				60 months
Bridge Loan | Line of Credit
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity				$ 10,000
Undrawn Letter Of Credit
Line of Credit Facility [Line Items]
Debt instrument, face amount					$ 10,000				$ 10,000