LEASES - Summary of Supplemental Balance Sheet Information (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Operating Leases:
Operating right-of-use assets	$ 154,929	$ 161,627
Lease Liabilities:
Current portion of operating lease liabilities	30,685	31,848
Long-term operating lease liabilities	128,714	136,054
Total operating lease liabilities	159,399	167,902
Finance Leases:
Property, plant and equipment, net	$ 18,068	$ 18,774
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	PROPERTY, PLANT AND EQUIPMENT, net	PROPERTY, PLANT AND EQUIPMENT, net
Lease Liabilities:
Lease liabilities, notes payable and current portion of long-term debt	$ 3,110	$ 3,352
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Notes payable and current portion of long-term debt	Notes payable and current portion of long-term debt
Lease liabilities, long-term debt, net	$ 14,950	$ 15,339
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:LongTermDebtNoncurrent	us-gaap:LongTermDebtNoncurrent
Total financing lease liabilities	$ 18,060	$ 18,691
Accumulated depreciation	$ 4,296	$ 2,383