Utility Regulatory Assets and Liabilities and Regulatory Matters - Narrative (Details) - USD ($) $ in Millions															12 Months Ended
	Oct. 06, 2023	Oct. 01, 2023	Sep. 21, 2023	Jul. 31, 2023	Mar. 06, 2023	Jan. 27, 2023	Nov. 16, 2022	Nov. 01, 2022	Oct. 29, 2022	Sep. 15, 2022	Jul. 29, 2022	Jan. 28, 2022	Nov. 09, 2021	Feb. 08, 2021	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Dec. 01, 2022	Oct. 19, 2016
Regulatory Assets [Line Items]
Regulatory asset, amortization period																			20 years
Unrealized gain (loss) on derivatives															$ (1,682)	$ 648	$ 1,398
Public Service Commission of West Virginia
Regulatory Assets [Line Items]
Under-recovery of gas cost																		$ 12
Public Service Commission of West Virginia | Mountaineer | 2023 Infrastructure Replacement and Expansion Plan
Regulatory Assets [Line Items]
Requested rate increase (decrease)				$ 10
Public Service Commission of West Virginia | Mountaineer | 2023 Infrastructure Replacement and Expansion Plan, Capital Improvement 2023
Regulatory Assets [Line Items]
Requested rate increase (decrease)				131
Public Service Commission of West Virginia | Mountaineer | 2023 Infrastructure Replacement and Expansion Plan, Capital Improvements 2024
Regulatory Assets [Line Items]
Requested rate increase (decrease)				67
Public Service Commission of West Virginia | Mountaineer | Net Revenue Increase
Regulatory Assets [Line Items]
Requested rate increase (decrease)					$ 20
Public Service Commission of West Virginia | Mountaineer | Net Revenue Increase | Subsequent Event
Regulatory Assets [Line Items]
Requested rate increase (decrease)	$ 14
Public Service Commission of West Virginia | Mountaineer | Base Rate Case, Base Rate
Regulatory Assets [Line Items]
Requested rate increase (decrease)					38
Public Service Commission of West Virginia | Mountaineer | Base Rate Case, Infrastructure Rider
Regulatory Assets [Line Items]
Requested rate increase (decrease)					$ (18)
Public Service Commission of West Virginia | Mountaineer | 2022 IREP For 2023 - 2027
Regulatory Assets [Line Items]
Requested rate increase (decrease)											$ 354
Public Service Commission of West Virginia | Mountaineer | 2022 IREP For 2023
Regulatory Assets [Line Items]
Requested rate increase (decrease)											$ 64
Public Service Commission of West Virginia | Mountaineer | 2023 IREP Revenue
Regulatory Assets [Line Items]
Requested rate increase (decrease)							$ 22
Public Service Commission of West Virginia | Mountaineer | 2021 IREP Recovery
Regulatory Assets [Line Items]
Requested rate increase (decrease)							$ 1
Public Service Commission of West Virginia | Mountaineer | 2023 Infrastructure Replacement and Expansion Plan, Capital Investments
Regulatory Assets [Line Items]
Requested rate increase (decrease)				383
Public Service Commission of West Virginia | Mountaineer | 2023 Infrastructure Replacement and Expansion Plan, Requested Recovery
Regulatory Assets [Line Items]
Requested rate increase (decrease)				6
Public Service Commission of West Virginia | Mountaineer | 2023 Infrastructure Replacement and Expansion Plan, Expected
Regulatory Assets [Line Items]
Requested rate increase (decrease)				$ (12)
Pennsylvania Public Utility Commission | Utilities
Regulatory Assets [Line Items]
Requested rate increase (decrease)						$ 11
Approved rate increase, amount			$ 9
Pennsylvania Public Utility Commission | Regulated natural gas utilities
Regulatory Assets [Line Items]
Requested rate increase (decrease)												$ 83
Pennsylvania Public Utility Commission | Regulated natural gas utilities | Joint Petition for Approval of Settlement
Regulatory Assets [Line Items]
Approved rate increase, amount										$ 49
Public utilities, rate period								5 years
Approved rate increase								3.00%
Property, plant and equipment, net threshold										$ 3,368
Pennsylvania Public Utility Commission | Regulated natural gas utilities | Joint Petition for Approval of Settlement, Phase I
Regulatory Assets [Line Items]
Approved rate increase, amount									$ 38
Pennsylvania Public Utility Commission | Regulated natural gas utilities | Joint Petition for Approval of Settlement, Phase II | Forecast
Regulatory Assets [Line Items]
Approved rate increase, amount		$ 11
Pennsylvania Public Utility Commission | Regulated natural gas utilities | Weather Normalization Adjustment Rider
Regulatory Assets [Line Items]
Public utilities, rate period								5 years
Approved rate increase								3.00%
Pennsylvania Public Utility Commission | UGI Gas
Regulatory Assets [Line Items]
Requested rate increase (decrease)														$ 9
Approved rate increase, amount													$ 6
Postretirement benefits
Regulatory Assets [Line Items]
Regulatory liability, amortization period																			10 years
Regulated natural gas utilities
Regulatory Assets [Line Items]
Unrealized gain (loss) on derivatives															$ (2)	$ 5
Minimum
Regulatory Assets [Line Items]
Average remaining depreciable lives of the associated property															1 year
Maximum
Regulatory Assets [Line Items]
Average remaining depreciable lives of the associated property															65 years
Maximum | Removal Costs, Net
Regulatory Assets [Line Items]
Regulatory asset, amortization period															5 years