LONG-TERM DEBT - Summary of long-term debt (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Outstanding Balance	$ 1,060,506	$ 1,064,422
less: Current portion	(12,486)	(9,922)
Long-term debt	1,048,020	1,054,500
Original Issuer Premium	315	363
less: Current portion	0	0
Non-current	315	363
Capitalized Fees & Expenses	(15,138)	(17,821)
Capitalized Fees & Expenses, Current	0	0
Capitalized Fees & Expenses, Noncurrent	(15,138)	(17,821)
Balance Sheet	1,045,683	1,046,964
less: Current portion	(12,486)	(9,922)
Long-term debt	1,033,197	1,037,042
Senior Notes Due 2028
Debt Instrument [Line Items]
Outstanding Balance	1,000,000	1,000,000
Original Issuer Premium	315	363
Capitalized Fees & Expenses	(13,293)	(15,376)
Balance Sheet	$ 987,022	$ 984,987
Coupon Interest Rate	5.75%	5.75%
Revolver Due 2025
Debt Instrument [Line Items]
Outstanding Balance	$ 13,483	$ 12,858
Original Issuer Premium	0	0
Capitalized Fees & Expenses	(1,718)	(2,209)
Balance Sheet	11,765	10,649
Finance Lease - Real Estate
Debt Instrument [Line Items]
Outstanding Balance	14,594	17,218
Original Issuer Premium	0	0
Capitalized Fees & Expenses	(4)	(30)
Balance Sheet	14,590	17,188
Non U.S. Lines of Credit
Debt Instrument [Line Items]
Outstanding Balance	3,012	0
Original Issuer Premium	0	0
Capitalized Fees & Expenses	(17)	(30)
Balance Sheet	2,995	(30)
Non U.S. Term Loans
Debt Instrument [Line Items]
Outstanding Balance	25,684	31,086
Original Issuer Premium	0	0
Capitalized Fees & Expenses	(91)	(160)
Balance Sheet	25,593	30,926
Other Long Term Debt
Debt Instrument [Line Items]
Outstanding Balance	3,733	3,260
Original Issuer Premium	0	0
Capitalized Fees & Expenses	(15)	(16)
Balance Sheet	$ 3,718	$ 3,244

Debt Issuance Costs, Current, Net

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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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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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