Income Taxes - Deferred Tax Liabilities (Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Excess book basis over tax basis of property, plant and equipment	$ 867	$ 937
Utility regulatory assets	106	105
Intangible assets and goodwill	75	77
Derivative instrument assets	514	322
Other	33	36
Gross deferred tax liabilities	1,595	1,477
Investment in AmeriGas Partners	(79)	(102)
Pension plan liabilities	(21)	(29)
Employee-related benefits	(38)	(45)
Operating loss carryforwards	(48)	(53)
Foreign tax credit carryforwards	(76)	(79)
Utility regulatory liabilities	(85)	(102)
Utility environmental liabilities	(15)	(16)
Other	(125)	(107)
Gross deferred tax assets	(487)	(533)
Deferred tax assets valuation allowance	141	138
Net deferred tax liabilities	$ 1,249	$ 1,082