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Rate And Regulatory Matters (Narrative-Illinois) (Details) - USD ($) $ in Millions | 1 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2023 | Nov. 30, 2023 | Oct. 31, 2023 | Jul. 31, 2023 | Dec. 31, 2027 | Dec. 31, 2026 | Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |
Capital expenditures |  |  |  |  |  |  |  |  | $ 3,597 | $ 3,351 | $ 3,479
Forecast |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |
Capital expenditures |  |  |  |  |  |  |  | $ 1,800 |  |  |
Ameren Illinois |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |
Capital expenditures |  |  |  |  |  |  |  |  | $ 1,731 | $ 1,601 | $ 1,432
Ameren Illinois | Minimum |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |
ICC required RTO cost benefit study duration |  |  |  | 5 years |  |  |  |  |  |  |
Ameren Illinois | Maximum |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |
ICC required RTO cost benefit study duration |  |  |  | 10 years |  |  |  |  |  |  |
Natural gas |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |
Percentage of energy sourced from renewable resources |  | 100.00% |  |  |  |  |  |  |  |  |
Natural gas | Ameren Illinois |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |
Percent of requested return on equity | 9.89% |  |  |  |  |  |  |  |  |  |
Percentage of requested equity capital structure | 52.00% |  |  |  |  |  |  |  |  |  |
IETL | Electric Distribution | Ameren Illinois |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |
Deadline to file a revised grid plan |  |  |  |  |  |  |  |  | 3 months |  |
IETL | Electric Distribution | Ameren Illinois | Forecast |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |
Multi-year rate plan approved revenue requirement |  |  |  |  | $ 1,255 | $ 1,242 | $ 1,210 | $ 1,162 |  |  |
Public Utilities, Approved Return on Equity, Percentage |  |  |  |  | 8.72% | 8.72% | 8.72% | 8.72% |  |  |
Public Utilities, Approved Equity Capital Structure, Percentage |  |  |  |  | 50.00% | 50.00% | 50.00% | 50.00% |  |  |
Approved rate base |  |  |  |  | $ 3,900 | $ 3,900 | $ 3,900 | $ 3,900 |  |  |
Multi-year rate plan requested revenue requirement |  |  |  |  | 1,420 | 1,371 | 1,300 | 1,214 |  |  |
American Illinois Proposed Average Annual Rate Base (in Billions) |  |  |  |  | $ 4,900 | $ 4,700 | $ 4,500 | 4,200 |  |  |
Approved rate increase (decrease), amount |  |  |  |  |  |  |  | 142 |  |  |
Cumulative rate increase |  |  |  |  |  |  |  | $ 444 |  |  |
Percent of requested return on equity |  |  |  |  |  |  |  | 9.82% |  |  |
IEIMA revenue requirement reconciliation adjustment | Ameren Illinois |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Return on Equity, Percentage |  |  |  |  |  |  |  |  | 5.80% |  |
Final Rate Order | Ameren Illinois |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |
Electric energy-efficiency revenue requirement |  | $ 100 |  |  |  |  |  |  |  |  |
Final Rate Order | Natural gas | Ameren Illinois |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Return on Equity, Percentage |  | 9.44% |  |  |  |  |  |  |  |  |
Public Utilities, Approved Equity Capital Structure, Percentage |  | 50.00% |  |  |  |  |  |  |  |  |
Approved rate base |  | $ 2,850 |  |  |  |  |  |  |  |  |
Cumulative rate increase |  | 112 |  |  |  |  |  |  |  |  |
Capital expenditures | $ 93 | $ 93 |  |  |  |  |  |  |  |  |
Pending Rate Case | Natural gas | Ameren Illinois |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |
Capital expenditures |  |  | $ 53 |  |  |  |  |  |  |  |
Amount of over-recovery challenged by the Attorney General |  |  | $ 3 |  |  |  |  |  |  |  |
IEIMA revenue requirement reconciliation adjustment | Final Rate Order | Electric Distribution | Ameren Illinois |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Equity Capital Structure, Percentage |  | 50.00% |  |  |  |  |  |  |  |  |
Approved rate base |  | $ 3,900 |  |  |  |  |  |  |  |  |
Approved rate increase (decrease), amount |  | 110 |  |  |  |  |  |  |  |  |
FEJA energy-efficiency rider | Final Rate Order | Ameren Illinois |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |
Approved rate base |  | 394 |  |  |  |  |  |  |  |  |
Approved rate increase (decrease), amount |  | $ 24 |  |  |  |  |  |  |  |  |

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