Income Taxes - Narrative (Details) - USD ($)	2 Months Ended	12 Months Ended
	Nov. 21, 2022	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Income Tax Examination [Line Items]
Foreign tax credits		$ 5,000,000	$ 0	$ 0
Foreign tax credit carryforwards		76,000,000	79,000,000
Net operating loss carryback			15,000,000	32,000,000
Income taxes receivable		128,000,000	128,000,000
GILTI taxes		3,000,000	8,000,000	0
Deferred tax assets relating to operating loss carryforwards		48,000,000	53,000,000
Increase (decrease) in valuation allowance		3,000,000	33,000,000
Unrecognized tax benefits if recognized would impact the reported effective tax rate		4,000,000	4,000,000	4,000,000
Future capital losses from PennEast and Hudson investments
Income Tax Examination [Line Items]
Increase (decrease) in valuation allowance			30,000,000
State Tax Rate Changes
Income Tax Examination [Line Items]
Increase (decrease) in valuation allowance		4,000,000
Future FTC's realizable
Income Tax Examination [Line Items]
Increase (decrease) in valuation allowance		6,000,000	10,000,000
Notional interest deduction carryover
Income Tax Examination [Line Items]
Increase (decrease) in valuation allowance		17,000,000	10,000,000
Foreign Net Operating Loss Carry Forwards
Income Tax Examination [Line Items]
Increase (decrease) in valuation allowance		4,000,000
AmeriGas Propane
Income Tax Examination [Line Items]
Operating loss carryforwards		6,000,000
Other Subsidiaries
Income Tax Examination [Line Items]
Deferred tax assets relating to operating loss carryforwards		48,000,000
Fiscal 2020 carryback to Fiscal 2015
Income Tax Examination [Line Items]
Income taxes receivable		90,000,000	37,000,000	90,000,000
Fiscal 2020 carryback to Fiscal 2015 | Subsequent Event
Income Tax Examination [Line Items]
Income tax refunds	$ 75,000,000
Foreign | Flaga
Income Tax Examination [Line Items]
Operating loss carryforwards		5,000,000
Foreign | UGI France
Income Tax Examination [Line Items]
Operating loss carryforwards		30,000,000
Foreign | Italy
Income Tax Examination [Line Items]
Foreign tax credit carryforwards			23,000,000
Foreign | Netherlands
Income Tax Examination [Line Items]
Operating loss carryforwards		10,000,000
Effects of tax rate changes – State, net of federal benefit
Income Tax Examination [Line Items]
Benefit from legislation		20,000,000
Decrease in income tax expense due to state tax flow through of accelerated depreciation		10,000,000	$ 9,000,000	$ 11,000,000
Operating loss carryforwards		787,000,000
Domestic | Mountaintop Energy Holding, LLC
Income Tax Examination [Line Items]
Operating loss carryforwards		$ 16,000,000