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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, 2024 | Dec. 31, 2023
--- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | $ 1,333 | $ 1,141
Excluded receivables, payables, and accrued income, net | 9 | 9
Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 911 | 787
Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 422 | 354
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 | 6 | 5
Commodity Contract |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 16 | 22
Nuclear Decommissioning Trust Fund | 1,333 | 1,141
Assets | 1,349 | 1,163
Derivative liabilities | 103 | 168
Commodity Contract | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 2
Nuclear Decommissioning Trust Fund | 911 | 787
Assets | 911 | 789
Derivative liabilities | 5 | 6
Commodity Contract | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 7 | 4
Nuclear Decommissioning Trust Fund | 422 | 354
Assets | 429 | 358
Derivative liabilities | 39 | 79
Commodity Contract | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 9 | 16
Nuclear Decommissioning Trust Fund | 0 | 0
Assets | 9 | 16
Derivative liabilities | 59 | 83
Ameren Missouri |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Assets | 1,343 | 1,160
Ameren Missouri | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Assets | 911 | 789
Ameren Missouri | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Assets | 426 | 357
Ameren Missouri | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Assets | 6 | 14
Ameren Missouri | Fuel oils |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 2
Derivative liabilities | 4 | 2
Ameren Missouri | Fuel oils | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 2
Derivative liabilities | 4 | 2
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 | 4 | 3
Derivative liabilities | 11 | 22
Ameren Missouri | Natural gas | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 0
Derivative liabilities | 0 | 0
Ameren Missouri | Natural gas | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 4 | 3
Derivative liabilities | 11 | 19
Ameren Missouri | Natural gas | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 0
Derivative liabilities | 0 | 3
Ameren Missouri | Power |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 6 | 5
Derivative liabilities | 0 | 1
Ameren Missouri | Power | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 0
Derivative liabilities | 0 | 0
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 | 6 | 5
Derivative liabilities | 0 | 1
Ameren Missouri | Uranium |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 9
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 | 0 | 9
Ameren Missouri | Commodity Contract |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 10 | 19
Derivative liabilities | 15 | 25
Ameren Missouri | Commodity Contract | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 2
Derivative liabilities | 4 | 2
Ameren Missouri | Commodity Contract | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 4 | 3
Derivative liabilities | 11 | 19
Ameren Missouri | Commodity Contract | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 6 | 14
Derivative liabilities | 0 | 4
Ameren Missouri | Equity securities | U.S. large capitalization |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 911 | 787
Ameren Missouri | Equity securities | U.S. large capitalization | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear Decommissioning Trust Fund | 911 | 787
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 | 191 | 150
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 | 191 | 150
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 | 145 | 136
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 | 145 | 136
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 | 86 | 68
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 | 86 | 68
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 | 6 | 3
Derivative liabilities | 35 | 75
Ameren Illinois | Natural gas | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 0
Derivative liabilities | 1 | 4
Ameren Illinois | Natural gas | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 3 | 1
Derivative liabilities | 28 | 60
Ameren Illinois | Natural gas | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 3 | 2
Derivative liabilities | 6 | 11
Ameren Illinois | Power |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative liabilities | 53 | 68
Ameren Illinois | Power | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative liabilities | 0 | 0
Ameren Illinois | Power | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative liabilities | 0 | 0
Ameren Illinois | Power | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative liabilities | 53 | 68
Ameren Illinois | Commodity Contract |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 6 | 3
Derivative liabilities | 88 | 143
Ameren Illinois | Commodity Contract | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 0
Derivative liabilities | 1 | 4
Ameren Illinois | Commodity Contract | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 3 | 1
Derivative liabilities | 28 | 60
Ameren Illinois | Commodity Contract | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 3 | 2
Derivative liabilities | $ 59 | $ 79

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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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