LEASES - RIGHT-OF-USE ASSETS AND LEASE LIABILITIES (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Sep. 30, 2023
Noncurrent
Operating lease assets	$ 177,176	$ 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	$ 27,168	$ 28,248
Total lease assets	204,344	203,988
Current
Operating lease liabilities	$ 4,780	$ 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	$ 8,816	$ 8,477
Noncurrent
Operating lease liabilities	$ 150,971	$ 148,023
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-term debt	Long-term debt
Finance lease liabilities	$ 18,661	$ 22,875
Total lease liabilities	$ 183,228	$ 184,147