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Contingencies and Legal Proceedings Legal Proceedings (Details) | 9 Months Ended |
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Jun. 30, 2020 USD ($) Agreements Groups Units | Sep. 30, 2019 USD ($)
Legal Proceedings |  |
Number of licensed nuclear units | Units | 7 |
Legal loss contingency accrual | $ 13,000,000 |
Amount paid for remediation under amended consent decree |  | $ 100,000
General |  |
Legal Proceedings |  |
Legal loss contingency accrual | $ 14,000,000 |
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 |
Accounts payable and accrued liabilities | General |  |
Legal Proceedings |  |
Legal loss contingency accrual | $ 30,000,000 |

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