LEASES - RIGHT-OF-USE ASSETS AND LEASE LIABILITIES (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Sep. 30, 2022
Noncurrent
Operating lease assets	$ 164,119	$ 168,520
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Utility plant, at cost	Utility plant, at cost
Finance lease assets	$ 28,788	$ 21,913
Total lease assets	192,907	190,433
Current
Operating lease liabilities	$ 5,273	$ 4,562
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Current maturities of long-term debt	Current maturities of long-term debt
Finance lease liabilities	$ 8,626	$ 6,538
Noncurrent
Operating lease liabilities	$ 135,916	$ 138,382
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-term debt	Long-term debt
Finance lease liabilities	$ 24,635	$ 23,752
Total lease liabilities	$ 174,450	$ 173,234