Leases - ROU Assets and Lease Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023
Assets
Finance leases	$ 44,748	$ 47,472
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Public Utilities, Property, Plant and Equipment, Net	Public Utilities, Property, Plant and Equipment, Net
Operating leases	$ 249,556	$ 223,366
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Deferred charges and other assets	Deferred charges and other assets
Total right-of-use assets	$ 294,304	$ 270,838
Current
Finance leases	$ 1,651	$ 1,568
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Current maturities of long-term debt	Current maturities of long-term debt
Operating leases	$ 34,340	$ 35,820
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other current liabilities	Other current liabilities
Noncurrent
Finance leases	$ 47,239	$ 48,825
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-term debt	Long-term debt
Operating leases	$ 224,498	$ 194,452
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Deferred credits and other liabilities	Deferred credits and other liabilities
Total	$ 307,728	$ 280,665