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Retirement Benefits (Summary Of Benefit Liability Recorded) (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022
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Defined Benefit Plan Disclosure [Line Items] |  |
Noncurrent asset | $ (551) | $ (377)
Ameren Missouri |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Noncurrent asset | (142) | (84)
Ameren Illinois |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Noncurrent asset | $ (351) | $ (263)

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- Definition Amount of asset (liability), recognized in statement of financial position, for defined benefit pension and other postretirement plans. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480535/715-20-45-2 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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