Summary of Significant Accounting Policies - Schedule of Depreciable Plant by Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Segment Reporting Information [Line Items]
Depreciable plant	$ 14,973,440	$ 13,998,897
Integrated Upstream and Gathering
Segment Reporting Information [Line Items]
Depreciable plant	9,151,025	8,417,495
Pipeline and Storage
Segment Reporting Information [Line Items]
Depreciable plant	3,003,944	2,919,506
Utility
Segment Reporting Information [Line Items]
Depreciable plant	2,801,821	2,645,981
All Other and Corporate
Segment Reporting Information [Line Items]
Depreciable plant	$ 16,650	$ 15,915