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Rate and Regulatory Matters (Narrative-Missouri) (Details) | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Nov. 30, 2023 USD ($) | Sep. 30, 2024 MWh | Dec. 31, 2023 MWh | Mar. 31, 2023 MWh | Dec. 31, 2022 MWh | Sep. 30, 2022 MWh | Dec. 31, 2027 USD ($) | Dec. 31, 2026 USD ($) | Dec. 31, 2025 USD ($) | Dec. 31, 2024 USD ($) MWh | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($)
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Capital expenditures |  |  |  |  |  |  |  |  |  | $ 4,319,000,000 | $ 3,597,000,000 | $ 3,351,000,000
Revenues |  |  |  |  |  |  |  |  |  | $ 7,623,000,000 | 7,500,000,000 | 7,957,000,000
Natural gas |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Percentage of energy sourced from renewable resources | 100.00% |  |  |  |  |  |  |  |  |  |  |
Ameren Missouri |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Amount of Megawatts | MWh |  |  |  |  |  |  |  |  |  | 102 |  |
Cass County, Boomtown, and Huck Finn Solar Project Purchase Price |  |  |  |  |  |  |  |  |  | $ 1,000,000,000 |  |
Capital expenditures |  |  |  |  |  |  |  |  |  | $ 2,712,000,000 | 1,760,000,000 | 1,690,000,000
Ameren Missouri | Rush Island Energy Center |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Costs to be securitized | $ 476,000,000 |  |  |  |  |  |  |  |  |  |  |
Amortization of regulatory asset | $ 15 |  |  |  |  |  |  |  |  |  |  |
Ameren Missouri | Solar generation facility |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Amount of Megawatts | MWh |  |  |  |  |  |  |  |  |  | 500 |  |
Ameren Missouri | Generation Facilities |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Capital expenditures |  |  |  |  |  |  |  |  |  | $ 1,700,000,000 |  |
Ameren Missouri | Maximum |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Percentage of energy sourced from renewable resources |  |  |  |  |  |  |  |  |  | 100.00% |  |
Ameren Missouri | Electric | Pending Rate Case |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Cumulative rate increase |  |  |  |  |  |  |  |  |  | $ 446,000,000 |  |
Percent of requested return on equity |  |  |  |  |  |  |  |  |  | 10.25% |  |
Percentage of requested equity capital structure |  |  |  |  |  |  |  |  |  | 52.00% |  |
American Missouri Proposed Average Annual Rate Base |  |  |  |  |  |  |  |  |  | $ 13,900,000,000 |  |
MoPSC Staff recommended rate increase (decrease) |  |  |  |  |  |  |  |  |  | $ 384,000,000 |  |
MoPSC Staff's recommended ROE |  |  |  |  |  |  |  |  |  | 9.74% |  |
MoPSC Staff's recommended capital structure |  |  |  |  |  |  |  |  |  | 52.00% |  |
MoPSC Staff's recommended rate base |  |  |  |  |  |  |  |  |  | $ 13,900,000,000 |  |
Months to complete a rate proceeding |  |  |  |  |  |  |  |  |  | 11 months |  |
Ameren Missouri | Electric | Minimum | Pending Rate Case |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Percentage of High Prairie costs challenged by the MoOPC |  |  |  |  |  |  |  |  |  | 25.00% |  |
Ameren Missouri | Electric | Maximum | Pending Rate Case |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Percentage of High Prairie costs challenged by the MoOPC |  |  |  |  |  |  |  |  |  | 45.00% |  |
Ameren Missouri | Build-transfer | Solar generation facility |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Amount of Megawatts | MWh |  |  | 300 |  | 200 | 150 |  |  |  |  |  |
Ameren Missouri | Development-transfer | Solar generation facility |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Amount of Megawatts | MWh |  |  | 150 |  |  |  |  |  |  |  |  |
Ameren Missouri | Self-build | Solar generation facility |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Amount of Megawatts | MWh |  |  | 50 | 50 |  |  |  |  |  |  |  |
Ameren Missouri | Self-build | Natural Gas Generation Facility |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Amount of Megawatts | MWh |  | 800 |  |  |  |  |  |  |  |  |  |
Ameren Missouri | Natural gas | Pending Rate Case |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Cumulative rate increase |  |  |  |  |  |  |  |  |  | $ 40,000,000 |  |
Percent of requested return on equity |  |  |  |  |  |  |  |  |  | 10.25% |  |
Percentage of requested equity capital structure |  |  |  |  |  |  |  |  |  | 52.00% |  |
American Missouri Proposed Average Annual Rate Base |  |  |  |  |  |  |  |  |  | $ 531,000,000 |  |
Months to complete a rate proceeding |  |  |  |  |  |  |  |  |  | 11 months |  |
Ameren Missouri | MEEIA 2019 | Electric |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  |  | $ 13,000,000 | $ 12,000,000 | $ 22,000,000
Ameren Missouri | MEEIA 2024 | Electric | Forecast |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Energy efficiency investments in MEEIA 2019 programs |  |  |  |  |  |  | $ 22,000,000 | $ 51,000,000 |  |  |  |
Percentage of MEEIA energy efficiency goals achieved |  |  |  |  |  |  |  | 100.00% |  |  |  |
Incentive award if energy efficiency goals are achieved |  |  |  |  |  |  | $ 2,000,000 | $ 5,000,000 | $ 5,000,000 |  |  |

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