Summary of Significant Accounting Policies - Average Depreciation, Depletion and Amortization Rates (Details) - uSDollarsPerMCFE		12 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Exploration And Production Operations
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization rate (in dollars per Mcfe of production)	[1]	0.61	0.69	0.63
Integrated Upstream and Gathering Other Operations
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		3.60%	3.60%	3.50%
Pipeline and Storage
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		2.60%	2.70%	2.60%
Utility
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		2.80%	2.80%	2.70%
All Other and Corporate
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		3.70%	3.00%	2.90%

[1] Amounts represents depletion of exploration and production properties.