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Supplemental Information (Schedule of Asset Retirement Obligations) (Details) - USD ($) $ in Millions | 6 Months Ended |
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Jun. 30, 2022 | Dec. 31, 2021
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] |  |
Asset Retirement Obligation, Beginning Balance | $ 764 |
Accretion | 15 |
Change in estimates | 2 |
Asset Retirement Obligation, Ending Balance | 781 |
Other current liabilities | 824 | $ 568
Union Electric Company |  |
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] |  |
Asset Retirement Obligation, Beginning Balance | 760 |
Accretion | 15 |
Change in estimates | 2 |
Asset Retirement Obligation, Ending Balance | 777 |
Other current liabilities | 134 | 116
Ameren Illinois Company |  |
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] |  |
Asset Retirement Obligation, Beginning Balance | 4 |
Accretion | 0 |
Change in estimates | 0 |
Asset Retirement Obligation, Ending Balance | 4 |
Other current liabilities | 277 | 251
Asset Retirement Obligation Balance |  |
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] |  |
Other current liabilities | 7 | 7
Asset Retirement Obligation Balance | Union Electric Company |  |
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] |  |
Other current liabilities | $ 7 | $ 7

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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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848 + Details
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- Definition Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 35 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6392603&loc=d3e7123-110846 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(4) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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