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Rate And Regulatory Matters (Narrative-Missouri) (Details) $ in Millions | 3 Months Ended
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Mar. 31, 2027 | Dec. 31, 2025 | Jun. 30, 2025 USD ($) | Mar. 31, 2025 USD ($) | Jun. 30, 2024 MWh | Mar. 31, 2024 USD ($) | Sep. 30, 2023 MWh | Dec. 31, 2022 MWh
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |
Depreciation and amortization |  |  |  | $ 367 |  | $ 361 |  |
Capital expenditures |  |  |  | $ 1,064 |  | 890 |  |
Union Electric Company |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |
PISA Deferral Percentage |  |  |  | 85.00% |  |  |  |
Depreciation and amortization |  |  |  | $ 194 |  | 195 |  |
Capital expenditures |  |  |  | $ 658 |  | $ 466 |  |
Union Electric Company | Maximum |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Percentage |  |  |  | 2.50% |  |  |  |
Union Electric Company | Maximum | Subsequent Event |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Percentage |  | 2.25% |  |  |  |  |  |
Union Electric Company | Generation Facilities |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |
Capital expenditures |  |  |  | $ 1,700 |  |  |  |
Union Electric Company | Electric | Subsequent Event |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |
Frequency of Integrated Resource Plan Filings | 4 years |  |  |  |  |  |  |
Union Electric Company | Electric | Final Rate Order | Subsequent Event |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Amount |  |  | $ 355 |  |  |  |  |
Depreciation and amortization |  |  | 70 |  |  |  |  |
Union Electric Company | Build-transfer | Solar generation facility |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |
Amount of Megawatts | MWh |  |  |  |  |  |  | 300 |
Union Electric Company | Self-build | Solar generation facility |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |
Amount of Megawatts | MWh |  |  |  |  |  |  | 50 | 50
Union Electric Company | Self-build | Natural Gas Generation Facility |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |
Amount of Megawatts | MWh |  |  |  |  | 800 |  |  |
Union Electric Company | Natural gas | Subsequent Event |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |
Number of days after end of test year to perform reconciliation when using a future test year | 45 days |  |  |  |  |  |  |
Union Electric Company | Natural gas | Pending Rate Case |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  |  |  | $ 38 |  |  |  |
Public Utilities, Requested Return on Equity, Percentage |  |  |  | 10.25% |  |  |  |
Public Utilities, Requested Equity Capital Structure, Percentage |  |  |  | 52.00% |  |  |  |
Rate Base |  |  |  | $ 525 |  |  |  |
Months to complete a rate proceeding |  |  |  | 11 months |  |  |  |
Union Electric Company | Natural gas | Pending Rate Case | Subsequent Event |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |
MoPSC Staff recommended rate increase (decrease) |  |  | $ 32 |  |  |  |  |
MoPSC Staff's recommended ROE |  |  | 9.64% |  |  |  |  |
MoPSC Staff's recommended capital structure |  |  | 52.00% |  |  |  |  |
MoPSC Staff's recommended rate base |  |  | $ 482 |  |  |  |  |

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