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Summary Of Significant Accounting Policies - Schedule of Other Assets and Other Liabilities (Details) - USD ($) $ in Millions | Dec. 31, 2025 | Dec. 31, 2024
--- | --- | ---
Accounting Policies [Line Items] |  |
Other current assets | $ 210 | $ 162
Regulatory Asset, Noncurrent | 2,524 | 2,397
Long-Term Debt, Current Maturities | 973 | 317
Interest accrued | 229 | 196
Long-Term Debt, Excluding Current Maturities | 18,214 | 17,262
Ameren Missouri Securitization Funding I, LLC |  |
Accounting Policies [Line Items] |  |
Unbilled Receivables, Not Billable | 2 | 0
Other current assets | 21 | 2
Regulatory Asset, Noncurrent | 443 | 465
Long-Term Debt, Current Maturities | 23 | 17
Interest accrued | 6 | 1
Current regulatory liabilities | 11 | 0
Long-Term Debt, Excluding Current Maturities | $ 426 | $ 448

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