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Commitments And Contingencies (Environmental Matters) (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2025 USD ($) energyCenter scrubber site | Dec. 31, 2024 USD ($) | Dec. 31, 2023 USD ($)
Other current liabilities | $ 570 | $ 475 |
Other deferred credits and liabilities | 540 | 487 |
Other operations and maintenance | 1,974 | 1,969 | $ 1,866
Asset Retirement Obligation | $ 854 | 827 | 791
Environmental Loss Contingency Statement Of Financial Position Extensible Enumeration Not Disclosed Flag | false |  |
Rush Island Energy Center Additional Mitigation Relief Ordered |  |  |
Other current liabilities | $ 36 | 40 |
Other deferred credits and liabilities |  | 24 |
Other operations and maintenance |  | 59 |
Ameren Missouri |  |  |
Number of Energy Center Scrubbers | scrubber | 2 |  |
Other current liabilities | $ 212 | 235 |
Other deferred credits and liabilities | 184 | 150 |
Other operations and maintenance | 1,029 | 1,050 | 1,003
Asset Retirement Obligation | $ 849 | 823 | 787
Number of Ameren Missouri Natural Gas Energy Centers Subject To IETL | energyCenter | 4 |  |
Ameren Missouri | Rush Island Energy Center Additional Mitigation Relief Ordered |  |  |
Other current liabilities | $ 36 | 40 |
Other deferred credits and liabilities |  | 24 |
Other operations and maintenance |  | 59 |
Ameren Illinois |  |  |
Other current liabilities | 227 | 172 |
Other deferred credits and liabilities | 268 | 273 |
Other operations and maintenance | 945 | 906 | 818
Asset Retirement Obligation | $ 5 | $ 4 | $ 4
Number of remediation sites | site | 3 |  |
Manufactured Gas Plant |  |  |
Accrual for environmental loss contingencies | $ 45 |  |
Manufactured Gas Plant | Ameren Illinois |  |  |
Number of remediation sites | site | 44 |  |
Accrual for environmental loss contingencies | $ 45 |  |
Minimum |  |  |
Estimated capital costs to comply with existing and known federal and state air emissions regulations | 70 |  |
Minimum | Ameren Missouri |  |  |
Estimated capital costs to comply with existing and known federal and state air emissions regulations | 70 |  |
Minimum | Manufactured Gas Plant | Ameren Illinois |  |  |
Estimate of possible loss | 45 |  |
Maximum |  |  |
Estimated capital costs to comply with existing and known federal and state air emissions regulations | 100 |  |
Maximum | Ameren Missouri |  |  |
Estimated capital costs to comply with existing and known federal and state air emissions regulations | 100 |  |
Maximum | Manufactured Gas Plant | Ameren Illinois |  |  |
Estimate of possible loss | 90 |  |
New CCR Rules Estimate |  |  |
Asset Retirement Obligation | 56 |  |
New CCR Rules Estimate | Ameren Missouri |  |  |
Asset Retirement Obligation | $ 56 |  |

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