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Rate And Regulatory Matters (Narrative-Illinois) (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Dec. 31, 2023 | Nov. 30, 2023 | Oct. 31, 2023 | Sep. 30, 2024 | Jun. 30, 2024 | Jun. 30, 2023 | Dec. 31, 2027 | Dec. 31, 2026 | Dec. 31, 2025 | Dec. 31, 2024
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Capital expenditures |  |  |  |  | $ 1,892 | $ 1,822 |  |  |  |
Ameren Illinois Company |  |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Capital expenditures |  |  |  |  | 717 | $ 844 |  |  |  |
Ameren Illinois Company | Natural gas |  |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Public Utilities, Requested Equity Capital Structure, Percentage | 52.00% |  |  |  |  |  |  |  |  |
Public Utilities, Requested Return on Equity, Percentage | 9.89% |  |  |  |  |  |  |  |  |
IETL | Ameren Illinois Company | Electric Distribution | Forecast |  |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Approved return on equity percentage |  |  |  |  |  |  | 8.72% | 8.72% | 8.72% | 8.72%
Multi-year rate plan rehearing approved revenue requirement |  |  |  |  |  |  | $ 1,397 | $ 1,350 | $ 1,282 | $ 1,196
Approved rate base |  |  |  |  |  |  | 4,700 | 4,500 | 4,300 | 4,000
Revised multi-year rate plan requested revenue requirement |  |  |  |  |  |  | 1,446 | 1,386 | 1,300 | 1,215
Revised multi-year rate plan requested rate base |  |  |  |  |  |  | 5,000 | 4,800 | 4,500 | 4,300
ICC staff revised multi-year rate plan recommended revenue requirement |  |  |  |  |  |  | 1,414 | 1,361 | 1,281 | 1,201
ICC staff revised multi-year rate plan recommended rate base |  |  |  |  |  |  | $ 4,800 | $ 4,600 | $ 4,400 | $ 4,200
Public Utilities, Approved Equity Capital Structure, Percentage |  |  |  |  |  |  | 50.00% | 50.00% | 50.00% | 50.00%
Public Utilities, Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  |  |  | $ 285
Public Utilities, Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  |  |  | 334
ICC staff recommended rate increase |  |  |  |  |  |  |  |  |  | $ 302
Pending Rate Case | Ameren Illinois Company | Electric Distribution |  |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
ICC staff recommended rate increase |  |  |  |  | 157 |  |  |  |  |
Pending Rate Case | Ameren Illinois Company | Electric Distribution | Subsequent Event |  |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  |  |  | $ 158 |  |  |  |  |  |
Public Utilities, Requested Equity Capital Structure, Percentage |  |  |  | 50.00% |  |  |  |  |  |
Pending Rate Case | Ameren Illinois Company | Electric Energy-Efficiency |  |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  |  |  |  | $ 26 |  |  |  |  |
Pending Rate Case | Ameren Illinois Company | Natural gas |  |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Capital expenditures |  |  | $ 53 |  |  |  |  |  |  |
Over-Recovery Challenged by the Attorney General |  |  | $ 3 |  |  |  |  |  |  |
Final Rate Order | Ameren Illinois Company | Natural gas |  |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Approved return on equity percentage |  | 9.44% |  |  |  |  |  |  |  |
Approved rate base |  | $ 2,850 |  |  |  |  |  |  |  |
Public Utilities, Approved Equity Capital Structure, Percentage |  | 50.00% |  |  |  |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  | $ 112 |  |  |  |  |  |  |  |
Capital expenditures | $ 93 | $ 93 |  |  |  |  |  |  |  |

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