LONG-TERM DEBT - Summary of interest expense incurred (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Debt Instrument [Line Items]
Cash Interest	$ 60,535	$ 62,883	$ 62,919
Amort. Debt Discount	(48)	122	270
Amort. Deferred Cost & Other Fees	2,688	3,539	5,123
Capitalized interest	(31)	(128)	(139)
Total Interest Expense	$ 63,175	$ 66,544	$ 68,312
Senior Notes Due 2028
Debt Instrument [Line Items]
Effective Interest Rate	5.95%	5.90%
Cash Interest	$ 57,500	$ 32,511
Amort. Debt Discount	(48)	0
Amort. Deferred Cost & Other Fees	2,084	1,072
Total Interest Expense	59,536	$ 33,583
Senior Notes Due 2022
Debt Instrument [Line Items]
Effective Interest Rate		5.67%	5.66%
Cash Interest		$ 22,816	$ 52,500
Amort. Debt Discount		122	270
Amort. Deferred Cost & Other Fees		1,735	3,803
Total Interest Expense		24,673	56,573
Revolver Due 2025
Debt Instrument [Line Items]
Cash Interest	1,078	5,866	6,998
Amort. Debt Discount	0	0	0
Amort. Deferred Cost & Other Fees	491	635	980
Total Interest Expense	$ 1,569	$ 6,501	$ 7,978
Finance Lease - Real Estate
Debt Instrument [Line Items]
Effective Interest Rate	5.65%	4.45%	6.70%
Cash Interest	$ 875	$ 386	$ 372
Amort. Debt Discount	0	0	0
Amort. Deferred Cost & Other Fees	25	25	25
Total Interest Expense	900	411	397
Non U.S. Lines of Credit
Debt Instrument [Line Items]
Cash Interest	15	12	19
Amort. Debt Discount	0	0	0
Amort. Deferred Cost & Other Fees	15	15	15
Total Interest Expense	30	27	34
Non U.S. Term Loans
Debt Instrument [Line Items]
Cash Interest	655	975	1,592
Amort. Debt Discount	0	0	0
Amort. Deferred Cost & Other Fees	71	55	109
Total Interest Expense	726	1,030	1,701
Other Long Term Debt
Debt Instrument [Line Items]
Cash Interest	443	445	640
Amort. Debt Discount	0	0	0
Amort. Deferred Cost & Other Fees	2	2	5
Total Interest Expense	$ 445	$ 447	$ 645
ESOP Loans
Debt Instrument [Line Items]
Effective Interest Rate			6.30%
Cash Interest			$ 937
Amort. Debt Discount			0
Amort. Deferred Cost & Other Fees			186
Total Interest Expense			$ 1,123