Contingencies and Legal Proceedings Legal Proceedings (Details)	3 Months Ended
Dec. 31, 2021 USD ($) Agreements Groups Units
Legal Proceedings
Number of licensed nuclear units \| Units	7
Amount remaining to be spent under environmental agreements [Abstract]	$ 10,000,000
Compensatory damages - Kingston Case	8,000,000
Punitive Damages - Kingston Case	10,000,000
Down payment from Nuclear Development	22,000,000
Compensated costs to Nuclear Development	1,000,000
Other Income	28,000,000
General
Legal Proceedings
Legal loss contingency accrual	$ 12,000,000
Environmental Agreements
Legal Proceedings
Number of similar environmental agreements entered into \| Agreements	2
Number of environmental agreements entered into with the EPA \| Agreements	1
Number of environmental agreements entered into with environmental advocacy groups \| Groups	3
Amount to be invested in certain TVA environmental projects	$ 290,000,000
Other long-term liabilities \| General
Legal Proceedings
Legal loss contingency accrual	11,000,000
Accounts payable and accrued liabilities \| General
Legal Proceedings
Legal loss contingency accrual	30,000,000
Other Current Liabilities \| General
Legal Proceedings
Legal loss contingency accrual	$ 1,000,000

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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Compensatory damages - Kingston Case

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Down payment from Nuclear Development

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Number of environmental agreements entered into with the EPA

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The number of licensed nuclear units owned.

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Number of similar environmental agreements entered into

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Number environmental advocacy groups with which there is an environmental agreement.

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Punitive Damages - Kingston Case

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Amount of loss contingency liability.

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Amount of revenue and income classified as other.

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