LONG-TERM DEBT - Summary of Interest Expense Incurred (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Debt Instrument [Line Items]
Cash interest, capitalized interest	$ (16)	$ (18)	$ (109)	$ (18)
Cash interest	16,121	15,996	46,936	47,200
Amort. Debt Discount	11	68	123	202
Amort. Debt Issuance Costs & Other Fees	593	1,224	2,748	3,932
Total Interest Expense	$ 16,725	17,288	$ 49,807	51,334
Senior notes due 2028
Debt Instrument [Line Items]
Effective Interest Rate	5.80%		5.90%
Cash interest, including amounts capitalized	$ 12,219	0	$ 17,785	0
Amort. Debt Discount	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	277	0	412	0
Total Interest Expense	$ 12,496	$ 0	$ 18,197	$ 0
Senior notes due 2022
Debt Instrument [Line Items]
Effective Interest Rate	6.20%	5.70%	5.70%	5.70%
Cash interest, including amounts capitalized	$ 1,960	$ 13,125	$ 23,125	$ 39,375
Amort. Debt Discount	11	68	123	202
Amort. Debt Issuance Costs & Other Fees	155	950	1,734	2,852
Total Interest Expense	2,126	14,143	24,982	42,429
Revolver due 2025
Debt Instrument [Line Items]
Cash interest, including amounts capitalized	1,597	2,282	4,798	4,846
Amort. Debt Discount	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	134	220	531	761
Total Interest Expense	1,731	$ 2,502	5,329	$ 5,607
ESOP Loans
Debt Instrument [Line Items]
Effective Interest Rate		7.20%		6.60%
Cash interest, including amounts capitalized	0	$ 0	0	$ 937
Amort. Debt Discount	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	0	0	0	186
Total Interest Expense	$ 0	$ 0	$ 0	$ 1,123
Capital lease - real estate
Debt Instrument [Line Items]
Effective Interest Rate	6.30%	5.60%	6.10%	5.50%
Cash interest, including amounts capitalized	$ 33	$ 78	$ 146	$ 294
Amort. Debt Discount	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	6	7	19	19
Total Interest Expense	39	85	165	313
Non US lines of credit
Debt Instrument [Line Items]
Cash interest, including amounts capitalized	4	4	11	15
Amort. Debt Discount	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	(1)	3	11	11
Total Interest Expense	3	7	22	26
Non US term loans
Debt Instrument [Line Items]
Cash interest, including amounts capitalized	222	376	786	1,273
Amort. Debt Discount	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	21	44	40	97
Total Interest Expense	243	420	826	1,370
Other long term debt
Debt Instrument [Line Items]
Cash interest, including amounts capitalized	102	149	394	478
Amort. Debt Discount	0	0	0	0
Amort. Debt Issuance Costs & Other Fees	1	0	1	6
Total Interest Expense	$ 103	$ 149	$ 395	$ 484