Goodwill and Intangible Assets - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023	Jun. 30, 2023
Goodwill [Line Items]
Impairment of goodwill	$ 0	$ 195,000,000	$ 656,000,000
Amortization expense of intangible assets	54,000,000	55,000,000	56,000,000
Fiscal 2026	47,000,000
Fiscal 2027	25,000,000
Fiscal 2028	16,000,000
Fiscal 2029	14,000,000
Fiscal 2030	$ 12,000,000
Senior Notes Due 2028 | Senior Notes | AmeriGas Partners and AmeriGas Finance Corp.
Goodwill [Line Items]
Principal amount				$ 500,000,000
Interest rate (as a percentage)				9.375%
AmeriGas Propane
Goodwill [Line Items]
Impairment of goodwill		$ 195,000,000	$ 656,000,000