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v3.23.3

Rate And Regulatory Matters (Narrative-Federal) (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended | 9 Months Ended
--- | --- | --- | ---
May 31, 2020 | Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022
Rate And Regulatory Matters [Line Items] |  |  |  |  |
ROE Change |  |  |  | 0.50% |
Revenues |  | $ 2,060 | $ 2,306 | $ 5,882 | $ 5,911
Ameren Illinois Company |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |
Revenues |  | $ 783 | $ 904 | 2,663 | $ 2,697
Midwest Independent Transmission System Operator, Inc |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |
Revenues |  |  |  | 19 |
Midwest Independent Transmission System Operator, Inc | Ameren Illinois Company |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |
Revenues |  |  |  | $ 13 |
Midwest Independent Transmission System Operator, Inc | Final Rate Order |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |
Approved return on equity percentage | 10.02% |  |  |  |

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