Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Income Tax Examination [Line Items]
Foreign tax credits	$ 17	$ 25	$ 5
Income taxes receivable	56	36
GILTI taxes	2	13	3
Deferred tax assets relating to operating loss carryforwards	72	75
Increase (decrease) in valuation allowance	(11)
Unrecognized tax benefits if recognized would impact the reported effective tax rate	18	26	5
Notional interest deduction carryover
Income Tax Examination [Line Items]
Increase (decrease) in valuation allowance	(22)	(5)
Capital Losses
Income Tax Examination [Line Items]
Increase (decrease) in valuation allowance	(4)	(22)
Future FTC's realizable
Income Tax Examination [Line Items]
Increase (decrease) in valuation allowance	(1)	(16)
Foreign Net Operating Loss Carry Forwards
Income Tax Examination [Line Items]
Increase (decrease) in valuation allowance	5	11
Disallowed Interest
Income Tax Examination [Line Items]
Increase (decrease) in valuation allowance	11	19
State Tax Rate Changes
Income Tax Examination [Line Items]
Increase (decrease) in valuation allowance		(3)
AmeriGas Propane
Income Tax Examination [Line Items]
Operating loss carryforwards	4
Other Subsidiaries
Income Tax Examination [Line Items]
Deferred tax assets relating to operating loss carryforwards	72
Effects of tax rate changes – State, net of federal benefit
Income Tax Examination [Line Items]
Benefit from legislation	12	4
Decrease in income tax expense due to state tax flow through of accelerated depreciation	12	11	$ 10
Operating loss carryforwards	1,223
Effects of U.S. tax legislation
Income Tax Examination [Line Items]
Income taxes receivable	56	36
Effects of U.S. tax legislation | Fiscal 2021
Income Tax Examination [Line Items]
Income taxes receivable	36	$ 36
Effects of tax rate changes - International | Administration of the Treasury, Belgium
Income Tax Examination [Line Items]
Operating loss carryforwards	8
Effects of tax rate changes - International | Tax and Customs Administration, Netherlands
Income Tax Examination [Line Items]
Operating loss carryforwards	66
Effects of tax rate changes - International | Flaga
Income Tax Examination [Line Items]
Operating loss carryforwards	9
Effects of tax rate changes - International | UGI France
Income Tax Examination [Line Items]
Operating loss carryforwards	$ 22