Utility Regulatory Assets and Liabilities and Regulatory Matters - Regulatory Assets and Liabilities Associated with Utilities (Details) - Utilities - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021
Regulatory Assets [Line Items]
Regulatory assets	$ 340	$ 397
Regulatory Liabilities [Line Items]
Regulatory liabilities	335	388
Postretirement benefits
Regulatory Liabilities [Line Items]
Regulatory liabilities	11	13
Deferred fuel and power refunds
Regulatory Liabilities [Line Items]
Regulatory liabilities	3	36
State income tax benefits — distribution system repairs
Regulatory Liabilities [Line Items]
Regulatory liabilities	38	32
Excess federal deferred income taxes
Regulatory Liabilities [Line Items]
Regulatory liabilities	279	287
Other
Regulatory Liabilities [Line Items]
Regulatory liabilities	4	20
Income taxes recoverable
Regulatory Assets [Line Items]
Regulatory assets	83	143
Underfunded pension plans
Regulatory Assets [Line Items]
Regulatory assets	114	108
Environmental costs
Regulatory Assets [Line Items]
Regulatory assets	37	58
Deferred fuel and power costs
Regulatory Assets [Line Items]
Regulatory assets	32	11
Removal costs, net
Regulatory Assets [Line Items]
Regulatory assets	22	24
Other
Regulatory Assets [Line Items]
Regulatory assets	$ 52	$ 53