LEASES - RIGHT-OF-USE ASSETS AND LEASE LIABILITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023
Noncurrent
Operating lease assets	$ 184,485	$ 175,740
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Utility plant, at cost	Utility plant, at cost
Finance lease assets	$ 26,088	$ 28,248
Total lease assets	210,573	203,988
Current
Operating lease liabilities	$ 4,945	$ 4,772
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	$ 7,534	$ 8,477
Noncurrent
Operating lease liabilities	$ 159,303	$ 148,023
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-term debt	Long-term debt
Finance lease liabilities	$ 16,026	$ 22,875
Total lease liabilities	$ 187,808	$ 184,147