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Supplemental Information (Schedule of Asset Retirement Obligations) (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2024 | Dec. 31, 2023
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] |  |
Asset Retirement Obligation, Beginning Balance | $ 791 |
Liabilities settled | (1) |
Accretion | 8 |
Asset Retirement Obligation, Ending Balance | 798 |
Other current liabilities | 651 | $ 648
Union Electric Company |  |
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] |  |
Asset Retirement Obligation, Beginning Balance | 787 |
Liabilities settled | 0 |
Accretion | 8 |
Asset Retirement Obligation, Ending Balance | 795 |
Other current liabilities | 206 | 222
Ameren Illinois Company |  |
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] |  |
Asset Retirement Obligation, Beginning Balance | 4 |
Liabilities settled | (1) |
Accretion | 0 |
Asset Retirement Obligation, Ending Balance | 3 |
Other current liabilities | 280 | 298
Asset Retirement Obligation Balance |  |
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] |  |
Other current liabilities | 19 | 19
Asset Retirement Obligation Balance | Union Electric Company |  |
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] |  |
Other current liabilities | $ 19 | $ 19

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- Definition The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 25 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481999/410-20-25-4 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481850/410-20-50-1 + Details
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- Definition Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481879/410-20-45-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481850/410-20-50-1 + Details
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- Definition Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481850/410-20-50-1 + Details
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