LONG-TERM DEBT - Summary of Interest Expense Incurred (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Cash Interest, Capitalized Interest	$ (7)	$ (65)
Cash Interest	15,010	14,939
Amort. Debt Discount	0	67
Amort. Debt Issuance Costs & Other Fees	680	1,205
Total Interest Expense	$ 15,690	16,211
Senior notes due 2028
Debt Instrument [Line Items]
Effective Interest Rate	5.40%
Cash Interest, Including Amounts Capitalized	$ 14,375	0
Amort. Debt Discount	0	0
Amort. Debt Issuance Costs & Other Fees	530	0
Total Interest Expense	14,905	$ 0
Senior notes due 2022
Debt Instrument [Line Items]
Effective Interest Rate		5.70%
Cash Interest, Including Amounts Capitalized	0	$ 13,125
Amort. Debt Discount	0	67
Amort. Debt Issuance Costs & Other Fees	0	951
Total Interest Expense	0	14,143
Revolver due 2025
Debt Instrument [Line Items]
Cash Interest, Including Amounts Capitalized	129	1,382
Amort. Debt Discount	0	0
Amort. Debt Issuance Costs & Other Fees	123	232
Total Interest Expense	252	$ 1,614
Finance lease - real estate
Debt Instrument [Line Items]
Effective Interest Rate		5.60%
Cash Interest, Including Amounts Capitalized	232	$ 61
Amort. Debt Discount	0	0
Amort. Debt Issuance Costs & Other Fees	6	6
Total Interest Expense	238	67
Non US lines of credit
Debt Instrument [Line Items]
Cash Interest, Including Amounts Capitalized	3	4
Amort. Debt Discount	0	0
Amort. Debt Issuance Costs & Other Fees	4	4
Total Interest Expense	7	8
Non US term loans
Debt Instrument [Line Items]
Cash Interest, Including Amounts Capitalized	171	272
Amort. Debt Discount	0	0
Amort. Debt Issuance Costs & Other Fees	17	12
Total Interest Expense	188	284
Other long term debt
Debt Instrument [Line Items]
Cash Interest, Including Amounts Capitalized	107	160
Amort. Debt Discount	0	0
Amort. Debt Issuance Costs & Other Fees	0	0
Total Interest Expense	$ 107	$ 160