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Rate And Regulatory Matters (Narrative-Missouri) (Details) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 USD ($) MWh | Jun. 30, 2025 MWh | Mar. 31, 2025 | Sep. 30, 2024 USD ($) | Jun. 30, 2024 MWh | Jun. 30, 2023 MWh | Mar. 31, 2023 MWh | Sep. 30, 2025 USD ($) MWh | Sep. 30, 2024 USD ($)
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Depreciation and amortization | $ 415 |  |  | $ 388 |  |  |  | $ 1,168 | $ 1,125
Capital expenditures |  |  |  |  |  |  |  | $ 3,118 | 3,029
Union Electric Company |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
PISA Deferral Percentage |  |  |  |  |  |  |  | 85.00% |
Depreciation and amortization | $ 239 |  |  | $ 220 |  |  |  | $ 642 | 623
Capital expenditures |  |  |  |  |  |  |  | 1,873 | $ 1,839
Union Electric Company | Maximum |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Percentage | 2.25% |  | 2.50% |  |  |  |  |  |
Union Electric Company | Natural Gas Generation Facility |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Capital expenditures |  |  |  |  |  |  |  | 900 |
Union Electric Company | Solar Generation Facilities |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Capital expenditures |  |  |  |  |  |  |  | $ 800 |
Union Electric Company | Electric |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Senate Bill 4 large service tariff threshold MWs | MWh |  |  |  |  |  |  |  | 100 |
Frequency of Integrated Resource Plan Filings |  |  |  |  |  |  |  | 4 years |
Large load customer rate plan megawatts requested | MWh |  |  |  |  |  |  |  | 75 |
Minimum service term for large load customer rate plan |  |  |  |  |  |  |  | 12 years |
Optional ramp up period for large load customer rate plan |  |  |  |  |  |  |  | 5 years |
Minimum demand charges as percentage of contracted capacity for large load customer rate plan |  |  |  |  |  |  |  | 80.00% |
Union Electric Company | Electric | Final Rate Order |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ 355 |
Depreciation and amortization |  |  |  |  |  |  |  | $ 70 |
Union Electric Company | Natural gas |  |  |  |  |  |  |  |  |
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 | Final Rate Order |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ 32 |
Union Electric Company | Self-build | Solar generation facility |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Amount of Megawatts | MWh | 250 |  |  |  |  | 50 | 50 |  |
Union Electric Company | Self-build | Natural Gas Generation Facility |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Amount of Megawatts | MWh |  | 800 |  |  | 800 |  |  |  |
Union Electric Company | Self-build | Energy Storage Facility |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Amount of Megawatts | MWh |  | 400 |  |  |  |  |  |  |
Union Electric Company | Build-transfer | Solar generation facility |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |
Amount of Megawatts | MWh |  |  |  |  |  | 300 |  |  |

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