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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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Carrying value as of the balance sheet date of [accrued] interest payable on all forms of debt, including trade payables, that has been incurred and is unpaid. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

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