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Rate and Regulatory Matters (Regulatory Framework-Missouri) (Details) - Ameren Missouri - USD ($) $ in Millions | 5 Months Ended | 7 Months Ended | 12 Months Ended
--- | --- | --- | ---
Dec. 31, 2025 | Jul. 31, 2025 | Dec. 31, 2025 | Dec. 31, 2024
Public Utilities, General Disclosures [Line Items] |  |  |  |
Number of months to complete a regulatory rate review |  |  | 11 months |
PISA deferral percentage |  |  | 85.00% |
Depreciation percentage not included in PISA deferral |  |  | 15.00% |
Sharing Level For Fac | 95.00% |  | 95.00% |
Percentage of variance not covered by FAC | 5.00% |  | 5.00% |
Base rate reset period |  |  | 4 years |
Rush Island Energy Center |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Regulatory asset, amortization period |  |  |  | 15 years
Costs to be securitized |  |  |  | $ 476
Maximum |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Percentage of energy sourced from renewable resources |  |  | 100.00% |
Public utilities, approved rate increase (decrease), percentage | 2.25% | 2.50% |  |
PISA |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Regulatory asset, amortization period | 20 years |  | 20 years |

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- Definition The portion of the variance in net energy costs from the amount set in base rates Ameren Missouri is permitted to recover or refund, through customer rates, without a traditional regulatory rate review. + References No definition available. + Details
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