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Fair Value Measurements (Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | $ 1,141 | $ 947
Excluded receivables, payables, and accrued income, net | 9 | 11
Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 787 | 618
Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 354 | 329
Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 0 | 0
Power | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 5 | 20
Commodity Contract |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 22 | 89
Nuclear Decommissioning Trust Fund | 1,141 | 947
Assets | 1,163 | 1,036
Derivative liabilities | 168 | 136
Commodity Contract | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 2 | 18
Nuclear Decommissioning Trust Fund | 787 | 618
Assets | 789 | 636
Derivative liabilities | 6 | 57
Commodity Contract | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 4 | 43
Nuclear Decommissioning Trust Fund | 354 | 329
Assets | 358 | 372
Derivative liabilities | 79 | 25
Commodity Contract | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 16 | 28
Nuclear Decommissioning Trust Fund | 0 | 0
Assets | 16 | 28
Derivative liabilities | 83 | 54
Ameren Missouri |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Assets | 1,160 | 996
Ameren Missouri | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Assets | 789 | 635
Ameren Missouri | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Assets | 357 | 344
Ameren Missouri | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Assets | 14 | 17
Ameren Missouri | Fuel oils |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 2 | 16
Derivative liabilities | 2 | 0
Ameren Missouri | Fuel oils | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 2 | 16
Derivative liabilities | 2 | 0
Ameren Missouri | Fuel oils | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 0
Derivative liabilities | 0 | 0
Ameren Missouri | Fuel oils | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 0
Derivative liabilities | 0 | 0
Ameren Missouri | Natural gas |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 3 | 16
Derivative liabilities | 22 | 9
Ameren Missouri | Natural gas | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 1
Derivative liabilities | 0 | 0
Ameren Missouri | Natural gas | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 3 | 15
Derivative liabilities | 19 | 6
Ameren Missouri | Natural gas | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 0
Derivative liabilities | 3 | 3
Ameren Missouri | Power |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 5 | 14
Derivative liabilities | 1 | 59
Ameren Missouri | Power | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 0
Derivative liabilities | 0 | 57
Ameren Missouri | Power | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 0
Derivative liabilities | 0 | 0
Ameren Missouri | Power | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 5 | 14
Derivative liabilities | 1 | 2
Ameren Missouri | Uranium |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 9 | 3
Ameren Missouri | Uranium | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 0
Ameren Missouri | Uranium | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 0
Ameren Missouri | Uranium | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 9 | 3
Ameren Missouri | Commodity Contract |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 19 | 49
Derivative liabilities | 25 | 68
Ameren Missouri | Commodity Contract | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 2 | 17
Derivative liabilities | 2 | 57
Ameren Missouri | Commodity Contract | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 3 | 15
Derivative liabilities | 19 | 6
Ameren Missouri | Commodity Contract | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 14 | 17
Derivative liabilities | 4 | 5
Ameren Missouri | Equity securities | U.S. large capitalization |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 787 | 618
Ameren Missouri | Equity securities | U.S. large capitalization | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 787 | 618
Ameren Missouri | Equity securities | U.S. large capitalization | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 0 | 0
Ameren Missouri | Equity securities | U.S. large capitalization | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 0 | 0
Ameren Missouri | Debt securities | U.S. Treasury and agency securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 150 | 137
Ameren Missouri | Debt securities | U.S. Treasury and agency securities | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 0 | 0
Ameren Missouri | Debt securities | U.S. Treasury and agency securities | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 150 | 137
Ameren Missouri | Debt securities | U.S. Treasury and agency securities | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 0 | 0
Ameren Missouri | Debt securities | Corporate bonds |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 136 | 122
Ameren Missouri | Debt securities | Corporate bonds | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 0 | 0
Ameren Missouri | Debt securities | Corporate bonds | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 136 | 122
Ameren Missouri | Debt securities | Corporate bonds | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 0 | 0
Ameren Missouri | Debt securities | Diversified credit |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 68 | 70
Ameren Missouri | Debt securities | Diversified credit | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 0 | 0
Ameren Missouri | Debt securities | Diversified credit | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 68 | 70
Ameren Missouri | Debt securities | Diversified credit | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 0 | 0
Ameren Illinois | Natural gas |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 3 | 34
Derivative liabilities | 75 | 29
Ameren Illinois | Natural gas | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 1
Derivative liabilities | 4 | 0
Ameren Illinois | Natural gas | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 1 | 28
Derivative liabilities | 60 | 19
Ameren Illinois | Natural gas | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 2 | 5
Derivative liabilities | 11 | 10
Ameren Illinois | Power |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 6
Derivative liabilities | 68 | 39
Ameren Illinois | Power | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 0
Derivative liabilities | 0 | 0
Ameren Illinois | Power | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 0
Derivative liabilities | 0 | 0
Ameren Illinois | Power | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 6
Derivative liabilities | 68 | 39
Ameren Illinois | Commodity Contract |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 3 | 40
Derivative liabilities | 143 | 68
Ameren Illinois | Commodity Contract | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 1
Derivative liabilities | 4 | 0
Ameren Illinois | Commodity Contract | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 1 | 28
Derivative liabilities | 60 | 19
Ameren Illinois | Commodity Contract | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 2 | 11
Derivative liabilities | $ 79 | $ 49

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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 + Details
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- Definition The fair value of investments held in a trust fund to pay for the costs of decontaminating and decommissioning facilities, whether such amount is presented as a separate caption or as a parenthetical disclosure on the balance sheet. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481850/410-20-50-1 + Details
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- Definition Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 210 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 22 -Publisher FASB -URI https://asc.fasb.org//1943274/2147483444/210-20-55-22 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483466/210-20-50-3 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 7 -Publisher FASB -URI https://asc.fasb.org//1943274/2147483444/210-20-55-7 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480434/815-10-50-4B Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 4D -Subparagraph (c)(2) -SubTopic 20 -Topic 860 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481326/860-20-50-4D + Details
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