LONG-TERM DEBT - Summary of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Sep. 30, 2021	Jun. 22, 2020
Debt Instrument [Line Items]
Long-term debt, Outstanding Balance	$ 1,067,596	$ 1,060,506
less: Current portion, Outstanding Balance	(15,675)	(12,486)
Long-term debt, Outstanding Balance, Non-current	1,051,921	1,048,020
Original Issuer Premium	302	315
less: Current portion, Original Issuer Premium	0	0
Long-term debt, Original Issuer Premium, Non-current	302	315
Capitalized Fees & Expenses	(14,468)	(15,138)
Long-term debt, Balance Sheet	1,053,430	1,045,683
less: Current portion, Balance Sheet	(15,675)	(12,486)
Long-term debt, Balance Sheet, Non-current	1,037,755	1,033,197
Senior notes due 2028
Debt Instrument [Line Items]
Long-term debt, Outstanding Balance	1,000,000	1,000,000
Original Issuer Premium	302	315
Capitalized Fees & Expenses	(12,775)	(13,293)
Long-term debt, Balance Sheet	$ 987,527	$ 987,022
Coupon Interest Rate	5.75%	5.75%	5.75%
Revolver due 2025
Debt Instrument [Line Items]
Long-term debt, Outstanding Balance	$ 19,859	$ 13,483
Original Issuer Premium	0	0
Capitalized Fees & Expenses	(1,595)	(1,718)
Long-term debt, Balance Sheet	18,264	11,765
Finance lease - real estate
Debt Instrument [Line Items]
Long-term debt, Outstanding Balance	14,083	14,594
Original Issuer Premium	0	0
Capitalized Fees & Expenses	0	(4)
Long-term debt, Balance Sheet	14,083	14,590
Non US lines of credit
Debt Instrument [Line Items]
Long-term debt, Outstanding Balance	6,533	3,012
Original Issuer Premium	0	0
Capitalized Fees & Expenses	(13)	(17)
Long-term debt, Balance Sheet	6,520	2,995
Non US term loans
Debt Instrument [Line Items]
Long-term debt, Outstanding Balance	23,761	25,684
Original Issuer Premium	0	0
Capitalized Fees & Expenses	(71)	(91)
Long-term debt, Balance Sheet	23,690	25,593
Other long term debt
Debt Instrument [Line Items]
Long-term debt, Outstanding Balance	3,360	3,733
Original Issuer Premium	0	0
Capitalized Fees & Expenses	(14)	(15)
Long-term debt, Balance Sheet	$ 3,346	$ 3,718

Amount of long term capitalized fees and expenses.

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The current portion of long term debt gross value.

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The carrying amount of long-term debt, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities).

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after accumulated amortization, of debt premium.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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