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Subsequent Events (Details) - USD ($) $ in Millions	Oct. 02, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2013	Sep. 30, 2012
Debt Instrument, Redemption [Line Items]
Non-current regulatory liabilities		$ 83	$ 107
Regulatory assets		9,408	5,566
Face Amount		40		$ 360
Long-term debt of variable interest entities, net		897	933
Current maturities of long-term debt of variable interest entities issued at par		37	35
JACTG
Debt Instrument, Redemption [Line Items]
Face Amount	$ 720
Long-term debt of variable interest entities, net	791
Current maturities of long-term debt of variable interest entities issued at par	9
Variable Interest Entity, Primary Beneficiary [Member]
Debt Instrument, Redemption [Line Items]
Debt and Lease Obligation	800
Holdco
Debt Instrument, Redemption [Line Items]
Face Amount	$ 80				$ 100
Unrealized gains/losses on commodity derivatives
Debt Instrument, Redemption [Line Items]
Regulatory assets		64	52
Unrealized gains/losses on commodity derivatives
Debt Instrument, Redemption [Line Items]
Non-current regulatory liabilities		$ 2	$ 12

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