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Rate And Regulatory Matters (Narrative-Missouri) (Details) | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Mar. 31, 2024 USD ($) | Nov. 30, 2023 USD ($) | Mar. 31, 2024 USD ($) | Jun. 30, 2023 MWh | Mar. 31, 2023 USD ($) | Sep. 30, 2022 MWh | Jun. 30, 2022 MWh | Mar. 31, 2022 MWh | Dec. 31, 2025 USD ($)
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Capital expenditures |  |  | $ 890,000,000 |  | $ 931,000,000 |  |  |  |
Union Electric Company |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Capital expenditures |  |  | 466,000,000 |  | $ 481,000,000 |  |  |  |
Union Electric Company | Rush Island Energy Center |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Costs to be Securitized |  | $ 519,000,000 |  |  |  |  |  |  |
Amortization of Regulatory Asset |  | $ 15 |  |  |  |  |  |  |
MoPSC Staff Recommended Costs to be Securitized | $ 497,000,000 |  |  |  |  |  |  |  |
Union Electric Company | Solar generation facility |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Capital expenditures |  |  | $ 850,000,000 |  |  |  |  |  |
Union Electric Company | Build-transfer | Solar generation facility |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Amount of Megawatts | MWh |  |  |  | 300 |  |  | 200 | 150 |
Union Electric Company | Development-transfer | Solar generation facility |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Amount of Megawatts | MWh |  |  |  | 150 |  |  |  |  |
Union Electric Company | Self-build | Solar generation facility |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Amount of Megawatts | MWh |  |  |  | 50 |  | 50 |  |  |
Union Electric Company | Electric | MEEIA 2024 | Forecast |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Energy efficiency investments in MEEIA 2019 programs |  |  |  |  |  |  |  |  | $ 123,000,000
Percentage of MEEIA Energy Efficiency Goals Achieved |  |  |  |  |  |  |  |  | 100.00%
Incentive award if energy efficiency goals are achieved |  |  |  |  |  |  |  |  | $ 56,000,000
Incentive award if energy efficiency goals are exceeded |  |  |  |  |  |  |  |  | $ 14,000,000

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