LEASES - RIGHT-OF-USE ASSETS AND LEASE LIABILITIES (Details) - USD ($) $ in Thousands |
Mar. 31, 2026 |
Sep. 30, 2025 |
|---|---|---|
| Noncurrent Assets | ||
| Operating lease assets | $ 188,223 | $ 185,596 |
| Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration] | Utility plant, at cost | Utility plant, at cost |
| Finance lease assets | $ 23,676 | $ 24,402 |
| Total lease assets | 211,899 | 209,998 |
| Current Liabilities | ||
| Operating lease liabilities | $ 5,168 | $ 4,388 |
| 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 | $ 4,614 | $ 5,568 |
| Noncurrent Liabilities | ||
| Operating lease liabilities | $ 163,048 | $ 159,131 |
| Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration] | Long-term debt | Long-term debt |
| Finance lease liabilities | $ 8,164 | $ 10,366 |
| Total lease liabilities | $ 180,994 | $ 179,453 |