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Supplemental Information (Schedule of Excise Taxes) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023
Accounting Policies [Line Items] |  |  |
Excise Tax Expense | $ 329 | $ 299 | $ 287
Ameren Missouri |  |  |
Accounting Policies [Line Items] |  |  |
Excise Tax Expense | 189 | 169 | 166
Ameren Illinois |  |  |
Accounting Policies [Line Items] |  |  |
Excise Tax Expense | $ 140 | $ 130 | $ 121

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- Definition The amount of excise and sales taxes included in sales and revenues, which are then deducted as a cost of sales. Includes excise taxes, which are applied to specific types of transactions or items (such as gasoline or alcohol); and sales, use and value added taxes, which are applied to a broad class of revenue-producing transactions involving a wide range of goods and services. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2 + Details
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