Summary Of Significant Accounting Policies - Schedule of Other Assets and Other Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Accounting Policies [Line Items]
Unbilled revenue	$ 511	$ 415
Other current assets	329	210
Regulatory Asset	2,964	2,524
Current maturities of long-term debt	1,574	973
Interest accrued	199	229
Long-term debt, net	20,443	18,214
Variable Interest Entity, Primary Beneficiary
Accounting Policies [Line Items]
Regulatory Asset	426	443
Current maturities of long-term debt	24	23
Long-term debt, net	414	426
Ameren Missouri Securitization Funding I, LLC \| Variable Interest Entity, Primary Beneficiary
Accounting Policies [Line Items]
Unbilled revenue	2	2
Other current assets	26	21
Regulatory Asset	426	443
Current maturities of long-term debt	24	23
Interest accrued	11	6
Current regulatory liabilities	5	11
Long-term debt, net	$ 414	$ 426

[Line Items] for Accounting Policies [Table]

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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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The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period.

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