LONG-TERM DEBT - Summary of Interest Expense Incurred (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Debt Instrument [Line Items]
Cash Interest, Capitalized Interest	$ (81)	$ (6)	$ (154)	$ (13)
Cash Interest	20,496	15,162	35,523	30,172
Amort. Debt (Premium)/Discount	18	(12)	6	(24)
Amort. Debt Issuance Costs & Other Fees	894	681	1,560	1,373
Total Interest Expense	$ 21,408	$ 15,831	$ 37,089	$ 31,521
Senior notes due 2028
Debt Instrument [Line Items]
Effective Interest Rate	6.00%	6.00%	6.00%	6.00%
Cash Interest, Including Amounts Capitalized	$ 14,375	$ 14,375	$ 28,750	$ 28,750
Amort. Debt (Premium)/Discount	(12)	(12)	(24)	(24)
Amort. Debt Issuance Costs & Other Fees	518	529	1,036	1,071
Total Interest Expense	$ 14,881	14,892	$ 29,762	29,797
Term Loan B 2029
Debt Instrument [Line Items]
Effective Interest Rate	3.40%		3.40%
Cash Interest, Including Amounts Capitalized	$ 4,767	0	$ 4,767	0
Amort. Debt (Premium)/Discount	30	0	30	0
Amort. Debt Issuance Costs & Other Fees	232	0	232	0
Total Interest Expense	5,029	0	5,029	0
Revolver due 2025
Debt Instrument [Line Items]
Cash Interest, Including Amounts Capitalized	990	287	1,251	416
Amort. Debt (Premium)/Discount	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	123	122	245	245
Total Interest Expense	$ 1,113	$ 409	$ 1,496	$ 661
Finance lease - real estate
Debt Instrument [Line Items]
Effective Interest Rate	5.60%	5.90%	5.50%	5.60%
Cash Interest, Including Amounts Capitalized	$ 192	$ 224	$ 390	$ 456
Amort. Debt (Premium)/Discount	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	0	7	4	13
Total Interest Expense	192	231	394	469
Non US lines of credit
Debt Instrument [Line Items]
Cash Interest, Including Amounts Capitalized	7	4	10	7
Amort. Debt (Premium)/Discount	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	3	4	7	8
Total Interest Expense	10	8	17	15
Non US term loans
Debt Instrument [Line Items]
Cash Interest, Including Amounts Capitalized	185	163	351	334
Amort. Debt (Premium)/Discount	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	18	18	35	35
Total Interest Expense	203	181	386	369
Other long term debt
Debt Instrument [Line Items]
Cash Interest, Including Amounts Capitalized	61	115	158	222
Amort. Debt (Premium)/Discount	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	0	1	1	1
Total Interest Expense	$ 61	$ 116	$ 159	$ 223

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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