Utility Regulatory Assets and Liabilities and Regulatory Matters - Narrative (Details) - USD ($) $ in Millions														9 Months Ended		12 Months Ended
	Jul. 31, 2024	Apr. 11, 2024	Dec. 21, 2023	Oct. 06, 2023	Sep. 21, 2023	Jul. 31, 2023	Mar. 06, 2023	Jan. 27, 2023	Jan. 01, 2023	Nov. 01, 2022	Sep. 15, 2022	Jul. 29, 2022	Jan. 28, 2022	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2023
Regulatory Assets
Net unrealized gains (losses)														$ (12)	$ (1,866)
Gas Utility
Regulatory Assets
Net unrealized gains (losses)														$ (1)	$ (7)	$ (2)
Utilities | PAPUC
Regulatory Assets
Requested rate increase (decrease)								$ 11					$ 83
Approved rate increase (decrease)					$ 9
Utilities | PAPUC | Joint Petition
Regulatory Assets
Requested rate increase (decrease)											$ 49
Property, plant and equipment, net threshold											3,368
Utilities | PAPUC | Beginning October 29, 2022
Regulatory Assets
Requested rate increase (decrease)											38
Utilities | PAPUC | Beginning October 1, 2023
Regulatory Assets
Requested rate increase (decrease)											$ 11
Utilities | PAPUC | Weather normalization adjustment rider
Regulatory Assets
Pilot program duration										5 years
Approved rate										3.00%
Mountaineer | WVPSC | Weather normalization adjustment rider
Regulatory Assets
Approved rate		2.00%
Adjustment rider period			5 years
Weather deviates threshold		2.00%
Mountaineer | WVPSC | 2024 IREP Recovery | Subsequent event
Regulatory Assets
Total capital investments	$ 418
Mountaineer | WVPSC | 2023 IREP Recovery
Regulatory Assets
Requested rate increase (decrease)						$ 10
Total capital investments						383
Mountaineer | WVPSC | 2023 IREP
Regulatory Assets
Costs associated with capital investments						131
Mountaineer | WVPSC | 2024 IREP For 2024 | Subsequent event
Regulatory Assets
Total capital investments	74
Mountaineer | WVPSC | 2023 IREP For 2024
Regulatory Assets
Costs associated with capital investments						$ 67
Mountaineer | WVPSC | Net Revenue Increase
Regulatory Assets
Requested rate increase (decrease)				$ 14			$ 20
Mountaineer | WVPSC | Base Rates
Regulatory Assets
Requested rate increase (decrease)							38
Mountaineer | WVPSC | IREP rate
Regulatory Assets
Requested rate increase (decrease)							$ (18)
Mountaineer | WVPSC | Over 2023 - 2027
Regulatory Assets
Requested rate increase (decrease)												$ 354
Mountaineer | WVPSC | Calendar Year 2023
Regulatory Assets
Requested rate increase (decrease)												$ 64
Approved rate increase (decrease)									$ 22
Mountaineer | WVPSC | 2024 Infrastructure Replacement and Expansion Plan, Prior Year Under-recovery | Subsequent event
Regulatory Assets
Requested rate increase (decrease)	3
Mountaineer | WVPSC | 2024 IREP Expected | Subsequent event
Regulatory Assets
Requested rate increase (decrease)	19
Total capital investments	$ 197