Summary of Significant Accounting Policies - Average Depreciation, Depletion and Amortization Rates (Details) - USD ($)		12 Months Ended
		Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Exploration and Production
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization rate (in dollars per Mcfe of production)	[1]	$ 0.71	$ 0.65	$ 0.59
Pipeline and Storage
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		2.70%	2.60%	2.70%
Gathering
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		3.60%	3.60%	3.60%
Utility
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		2.80%	2.70%	2.70%
All Other and Corporate
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		3.00%	2.90%	1.40%
Exploration and Production Properties
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization rate (in dollars per Mcfe of production)		$ 0.69	$ 0.63	$ 0.57

[1] Amounts include depletion of exploration and production properties as well as depreciation of fixed assets. As disclosed in Note N — Supplementary Information for Exploration and Production Activities, depletion of exploration and production properties amounted to $0.69, $0.63 and $0.57 per Mcfe of production in 2024, 2023 and 2022, respectively.