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Rate And Regulatory Matters (Narrative-Illinois) (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Dec. 31, 2023 | Nov. 30, 2023 | Oct. 31, 2023 | Jun. 30, 2024 | Mar. 31, 2024 | Mar. 31, 2023 | Dec. 31, 2027 | Dec. 31, 2026 | Dec. 31, 2025 | Dec. 31, 2024
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Capital expenditures |  |  |  |  | $ 890 | $ 931 |  |  |  |
Ameren Illinois Company |  |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Capital expenditures |  |  |  |  | $ 373 | $ 407 |  |  |  |
Ameren Illinois Company | Natural gas |  |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Public Utilities, Requested Return on Equity, Percentage | 9.89% |  |  |  |  |  |  |  |  |
Public Utilities, Requested Equity Capital Structure, Percentage | 52.00% |  |  |  |  |  |  |  |  |
IETL | Ameren Illinois Company | Electric Distribution | Forecast |  |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Multi-year rate plan rehearing requested revenue requirement |  |  |  |  |  |  |  |  |  | $ 1,213
Multi-year rate plan rehearing requested rate base |  |  |  |  |  |  |  |  |  | $ 4,200
Public Utilities, Approved Equity Capital Structure, Percentage |  |  |  |  |  |  | 50.00% | 50.00% | 50.00% | 50.00%
Approved return on equity percentage |  |  |  |  |  |  | 8.72% | 8.72% | 8.72% | 8.72%
ICC staff multi-year rate plan rehearing recommended revenue requirement |  |  |  |  |  |  |  |  |  | $ 1,195
ICC staff multi-year rate plan rehearing recommended rate base |  |  |  |  |  |  |  |  |  | 4,000
Multi-year rate plan approved revenue requirement |  |  |  |  |  |  | $ 1,255 | $ 1,242 | $ 1,210 | 1,162
Approved rate base |  |  |  |  |  |  | 3,900 | 3,900 | 3,900 | 3,900
Multi-year rate plan requested revenue requirement |  |  |  |  |  |  | 1,433 | 1,371 | 1,286 | 1,207
Multi-year rate plan requested rate base |  |  |  |  |  |  | $ 4,900 | $ 4,700 | $ 4,400 | $ 4,200
Public Utilities, Requested Return on Equity, Percentage |  |  |  |  |  |  | 9.24% | 9.24% | 9.24% | 9.24%
Public Utilities, Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  |  |  | $ 142
Public Utilities, Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  |  |  | $ 321
Pending Rate Case | Ameren Illinois Company | Electric Distribution | Subsequent Event |  |  |  |  |  |  |  |  |  |
Rate And Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  |  |  | $ 160 |  |  |  |  |  |
Public Utilities, Requested Equity Capital Structure, Percentage |  |  |  | 50.00% |  |  |  |  |  |
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] |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Equity Capital Structure, Percentage |  | 50.00% |  |  |  |  |  |  |  |
Approved return on equity percentage |  | 9.44% |  |  |  |  |  |  |  |
Approved rate base |  | $ 2,850 |  |  |  |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  | 112 |  |  |  |  |  |  |  |
Capital expenditures | $ 93 | $ 93 |  |  |  |  |  |  |  |

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