Financial Instruments - Schedule of Derivative Instruments in Statement of Financial Position, Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Sep. 30, 2023
Derivatives Fair Value [Line Items]
Gross/net financial instruments, assets	$ 381,220	$ 385,664
Gross/net financial instruments, liabilities	(5,977)	(15,408)
Designated As Hedges:
Derivatives Fair Value [Line Items]
Gross/net financial instruments, assets	377,600	379,101
Gross/net financial instruments, liabilities	0	0
Designated As Hedges: | Other current assets | Interest rate contracts
Derivatives Fair Value [Line Items]
Gross/net financial instruments, assets	273,551
Designated As Hedges: | Other current liabilities | Interest rate contracts
Derivatives Fair Value [Line Items]
Gross/net financial instruments, liabilities	0
Designated As Hedges: | Deferred charges and other assets | Interest rate contracts
Derivatives Fair Value [Line Items]
Gross/net financial instruments, assets	104,049	379,101
Designated As Hedges: | Deferred credits and other liabilities | Interest rate contracts
Derivatives Fair Value [Line Items]
Gross/net financial instruments, liabilities	0	0
Not Designated As Hedges:
Derivatives Fair Value [Line Items]
Gross/net financial instruments, assets	3,620	6,563
Gross/net financial instruments, liabilities	(5,977)	(15,408)
Not Designated As Hedges: | Other current assets | Commodity contracts
Derivatives Fair Value [Line Items]
Gross/net financial instruments, assets	2,349	4,071
Not Designated As Hedges: | Other current liabilities | Commodity contracts
Derivatives Fair Value [Line Items]
Gross/net financial instruments, liabilities	(5,928)	(14,584)
Not Designated As Hedges: | Deferred charges and other assets | Commodity contracts
Derivatives Fair Value [Line Items]
Gross/net financial instruments, assets	1,271	2,492
Not Designated As Hedges: | Deferred credits and other liabilities | Commodity contracts
Derivatives Fair Value [Line Items]
Gross/net financial instruments, liabilities	$ (49)	$ (824)