Summary of Significant Accounting Policies - Reclassification Out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Reclassification Adjustment out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating Revenues		$ 1,944,810	$ 2,173,771	$ 2,186,046
Total Before Income Tax		87,255	641,399	682,650
Income Tax Expense		(9,742)	(164,533)	(116,629)
Net of Tax		77,513	476,866	$ 566,021
Amount of Gain or (Loss) Reclassified From Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Before Income Tax		214,148	(90,330)
Income Tax Expense		(61,550)	6,217
Net of Tax		152,598	(84,113)
Amount of Gain or (Loss) Reclassified From Accumulated Other Comprehensive Income (Loss) | Amortization of Prior Year Funded Status of the Pension and Other Post-Retirement Benefit Plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Prior Service Cost	[1]	(56)	(82)
Net Actuarial Loss	[1]	(2,451)	(1,592)
Commodity Contracts | Amount of Gain or (Loss) Reclassified From Accumulated Other Comprehensive Income (Loss) | Gains (Losses) on Derivative Financial Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating Revenues		217,012	(88,015)
Foreign Currency Contracts | Amount of Gain or (Loss) Reclassified From Accumulated Other Comprehensive Income (Loss) | Gains (Losses) on Derivative Financial Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating Revenues		$ (357)	$ (641)

[1] These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. Refer to Note K — Retirement Plan and Other Post-Retirement Benefits for additional details.