Utility Regulatory Assets and Liabilities and Regulatory Matters - Schedule of Regulatory Assets and Liabilities (Details) - Utilities - USD ($) $ in Millions	Jun. 30, 2023	Sep. 30, 2022	Jun. 30, 2022
Regulatory Assets
Regulatory assets	$ 350	$ 340	$ 371
Regulatory Liabilities
Regulatory liabilities	376	335	336
Postretirement benefit overcollections
Regulatory Liabilities
Regulatory liabilities	10	11	12
Deferred fuel and power refunds
Regulatory Liabilities
Regulatory liabilities	63	3	1
State tax benefits — distribution system repairs
Regulatory Liabilities
Regulatory liabilities	40	38	34
Excess federal deferred income taxes
Regulatory Liabilities
Regulatory liabilities	260	279	281
Other
Regulatory Liabilities
Regulatory liabilities	3	4	8
Income taxes recoverable
Regulatory Assets
Regulatory assets	95	83	151
Underfunded pension plans
Regulatory Assets
Regulatory assets	118	114	103
Environmental costs
Regulatory Assets
Regulatory assets	28	37	34
Deferred fuel and power costs
Regulatory Assets
Regulatory assets	30	32	14
Removal costs, net
Regulatory Assets
Regulatory assets	22	22	22
Other
Regulatory Assets
Regulatory assets	$ 57	$ 52	$ 47