Equity Method Investments - Narrative (Details) $ in Millions	1 Months Ended			3 Months Ended	12 Months Ended
	Jan. 31, 2023 MMBTU MW	Jun. 30, 2021 USD ($)	Feb. 28, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) owner mi	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)
Schedule of Equity Method Investments [Line Items]
Carrying Value				$ 130	$ 299	$ 130	$ 174
Equity in (loss) income of unconsolidated subsidiaries					2	$ (14)	$ (63)
Pine Run
Schedule of Equity Method Investments [Line Items]
Total purchase price			$ 205
Total cash paid			115
Liabilities incurred			$ 90
Pennant
Schedule of Equity Method Investments [Line Items]
Effective ownership interest in AmeriGas OLP (as a percentage)				47.00%		47.00%
Total purchase price				$ 61
Percentage of voting interests acquired				53.00%		53.00%
Other-than-temporary pre-tax impairment charge				$ 44
Aurum Renewables
Schedule of Equity Method Investments [Line Items]
Landfill gas units | MW	11
Effective ownership interest in AmeriGas OLP (as a percentage)	40.00%
Expected production capacity per day | MMBTU	5,000
Energy Services | Pennant
Schedule of Equity Method Investments [Line Items]
Percentage of voting interests acquired				53.00%		53.00%
PennEast Pipeline Company, LLC
Schedule of Equity Method Investments [Line Items]
Pretax impairment charge		$ 93
Equity in (loss) income of unconsolidated subsidiaries						$ 9
PennEast Pipeline Company, LLC | Level 2
Schedule of Equity Method Investments [Line Items]
Carrying Value				$ 0	$ 0	0
PennEast Pipeline Company, LLC | Affiliated Entity
Schedule of Equity Method Investments [Line Items]
Area of natural gas pipeline to be constructed (in miles) | mi					120
Pennant | Affiliated Entity
Schedule of Equity Method Investments [Line Items]
Ownership Interest					20.00%
Number of other members | owner					4
Other
Schedule of Equity Method Investments [Line Items]
Pretax impairment charge					$ 55	$ 39