Summary of Significant Accounting Policies - Reclassification Out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating Revenues		$ 2,277,541	$ 1,944,810	$ 2,173,771
Total Before Income Tax		694,053	87,255	641,399
Income Tax Expense	[1]	(175,549)	(9,742)	(164,533)
Net of Tax		518,504	77,513	$ 476,866
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		41,639	214,148
Income Tax Expense		(11,349)	(61,550)
Net of Tax		30,290	152,598
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	[2]	(42)	(56)
Net Actuarial Loss	[2]	(4,210)	(2,451)
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		46,957	217,012
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		$ (1,066)	$ (357)

[1] The Company considers this line to be a significant expense.

[2] 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.