LONG-TERM DEBT - Summary of Interest Expense Incurred (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Debt Instrument [Line Items]
Cash Interest, Capitalized Interest	$ 0	$ (16)	$ (13)	$ (109)
Cash Interest	15,214	16,121	45,386	46,936
Amort. Debt Premium	(12)	11	(35)	123
Amort. Debt Issuance Costs & Other Fees	647	593	2,019	2,748
Total Interest Expense	$ 15,849	$ 16,725	$ 47,370	$ 49,807
Senior notes due 2028
Debt Instrument [Line Items]
Effective Interest Rate	6.00%	5.80%	6.00%	5.90%
Cash Interest, Including Amounts Capitalized	$ 14,375	$ 12,219	$ 43,125	$ 17,785
Amort. Debt Premium	(12)	0	(35)	0
Amort. Debt Issuance Costs & Other Fees	496	277	1,566	412
Total Interest Expense	14,859	$ 12,496	44,656	$ 18,197
Senior notes due 2022
Debt Instrument [Line Items]
Effective Interest Rate		5.70%		5.70%
Cash Interest, Including Amounts Capitalized	0	$ 1,960	0	$ 23,125
Amort. Debt Premium	0	11	0	123
Amort. Debt Issuance Costs & Other Fees	0	155	0	1,734
Total Interest Expense	0	2,126	0	24,982
Revolver due 2025
Debt Instrument [Line Items]
Cash Interest, Including Amounts Capitalized	344	1,597	760	4,798
Amort. Debt Premium	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	123	134	368	531
Total Interest Expense	$ 467	$ 1,731	$ 1,128	$ 5,329
Finance lease - real estate
Debt Instrument [Line Items]
Effective Interest Rate	5.80%	6.30%	5.80%	6.10%
Cash Interest, Including Amounts Capitalized	$ 215	$ 33	$ 671	$ 146
Amort. Debt Premium	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	6	6	19	19
Total Interest Expense	221	39	690	165
Non US lines of credit
Debt Instrument [Line Items]
Cash Interest, Including Amounts Capitalized	4	4	11	11
Amort. Debt Premium	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	4	(1)	12	11
Total Interest Expense	8	3	23	22
Non US term loans
Debt Instrument [Line Items]
Cash Interest, Including Amounts Capitalized	169	222	503	786
Amort. Debt Premium	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	18	21	53	40
Total Interest Expense	187	243	556	826
Other long term debt
Debt Instrument [Line Items]
Cash Interest, Including Amounts Capitalized	107	102	329	394
Amort. Debt Premium	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	0	1	1	1
Total Interest Expense	$ 107	$ 103	$ 330	$ 395

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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