Commitments and Contingencies - Legal Proceedings (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2022	Sep. 30, 2021
Legal Proceedings
Possible additional future costs for compliance with CCR requirements	$ 900
Contribution related to TVARS case	4	$ 5
Possible additional future costs for compliance with Clean Water requirements.	111
Amount remaining to be spent under environmental agreements	9
Loss Contingency, Damages Sought, Value	30
Down payment from Nuclear Development	22
Compensated costs to Nuclear Development	1
General
Legal Proceedings
Legal loss contingency accrual	11
Environmental Agreements
Legal Proceedings
Amount to be invested in certain environmental projects	290
Amount invested in certain environmental projects	282
Other long-term liabilities \| General
Legal Proceedings
Legal loss contingency accrual	10
Accounts payable and accrued liabilities \| General
Legal Proceedings
Legal loss contingency accrual	$ 1

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Amount remaining to be spent under environmental agreements

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Amount to be invested in certain environmental projects

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Compensated costs to Nuclear Development

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Down payment from Nuclear Development

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The possible additional future costs for compliance with CCR requirements

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The possible additional future costs for compliance with Clean Water requirements.

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Amount of loss contingency liability.

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The value (monetary amount) of the award the plaintiff seeks in the legal matter.

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Amount of cash outflow for pension and other postretirement benefits. Includes, but is not limited to, employer contribution to fund plan asset and payment to retiree.

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