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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 | Mar. 31, 2025 | Dec. 31, 2024
--- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | $ 1,304 | $ 1,333
Assets fair value | 1,331 | 1,349
Excluded receivables, payables, and accrued income, net | 8 | 9
Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 868 | 911
Assets fair value | 870 | 911
Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 436 | 422
Assets fair value | 450 | 429
Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 0 | 0
Assets fair value | 11 | 9
Commodity Contract |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 27 | 16
Derivative Liability | 99 | 103
Commodity Contract | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 2 | 0
Derivative Liability | 3 | 5
Commodity Contract | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 14 | 7
Derivative Liability | 25 | 39
Commodity Contract | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 11 | 9
Derivative Liability | 71 | 59
Union Electric Company |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 1,304 | 1,333
Assets fair value | 1,315 | 1,343
Union Electric Company | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 868 | 911
Assets fair value | 868 | 911
Union Electric Company | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 436 | 422
Assets fair value | 441 | 426
Union Electric Company | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 0 | 0
Assets fair value | 6 | 6
Union Electric Company | Commodity Contract |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 11 | 10
Derivative Liability | 12 | 15
Union Electric Company | Commodity Contract | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 0 | 0
Derivative Liability | 3 | 4
Union Electric Company | Commodity Contract | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 5 | 4
Derivative Liability | 8 | 11
Union Electric Company | Commodity Contract | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 6 | 6
Derivative Liability | 1 | 0
Union Electric Company | Fuel oils | Commodity Contract |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Liability | 3 | 4
Union Electric Company | Fuel oils | Commodity Contract | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Liability | 3 | 4
Union Electric Company | Fuel oils | Commodity Contract | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Liability | 0 | 0
Union Electric Company | Fuel oils | Commodity Contract | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Liability | 0 | 0
Union Electric Company | Natural gas | Commodity Contract |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 6 | 4
Derivative Liability | 9 | 11
Union Electric Company | Natural gas | Commodity Contract | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 0 | 0
Derivative Liability | 0 | 0
Union Electric Company | Natural gas | Commodity Contract | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 5 | 4
Derivative Liability | 8 | 11
Union Electric Company | Natural gas | Commodity Contract | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 1 | 0
Derivative Liability | 1 | 0
Union Electric Company | Power | Commodity Contract |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 5 | 6
Union Electric Company | Power | Commodity Contract | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 0 | 0
Union Electric Company | Power | Commodity Contract | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 0 | 0
Union Electric Company | Power | Commodity Contract | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 5 | 6
Union Electric Company | Equity securities: | U.S. large capitalization |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 868 | 911
Union Electric Company | Equity securities: | U.S. large capitalization | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 868 | 911
Union Electric Company | Equity securities: | U.S. large capitalization | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 0 | 0
Union Electric Company | Equity securities: | U.S. large capitalization | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 0 | 0
Union Electric Company | Debt securities: | U.S. Treasury and agency securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 188 | 191
Union Electric Company | 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
Union Electric Company | Debt securities: | U.S. Treasury and agency securities | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 188 | 191
Union Electric Company | 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
Union Electric Company | Debt securities: | Corporate bonds |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 156 | 145
Union Electric Company | Debt securities: | Corporate bonds | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 0 | 0
Union Electric Company | Debt securities: | Corporate bonds | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 156 | 145
Union Electric Company | Debt securities: | Corporate bonds | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 0 | 0
Union Electric Company | Debt securities: | Other Debt Securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 92 | 86
Union Electric Company | Debt securities: | Other Debt Securities | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 0 | 0
Union Electric Company | Debt securities: | Other Debt Securities | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 92 | 86
Union Electric Company | Debt securities: | Other Debt Securities | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Nuclear decommissioning trust fund: | 0 | 0
Ameren Illinois Company |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Assets fair value | 16 | 6
Ameren Illinois Company | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Assets fair value | 2 | 0
Ameren Illinois Company | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Assets fair value | 9 | 3
Ameren Illinois Company | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Assets fair value | 5 | 3
Ameren Illinois Company | Commodity Contract |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Liability | 87 | 88
Ameren Illinois Company | Commodity Contract | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Liability | 0 | 1
Ameren Illinois Company | Commodity Contract | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Liability | 17 | 28
Ameren Illinois Company | Commodity Contract | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Liability | 70 | 59
Ameren Illinois Company | Natural gas | Commodity Contract |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 16 | 6
Derivative Liability | 20 | 35
Ameren Illinois Company | Natural gas | Commodity Contract | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 2 | 0
Derivative Liability | 0 | 1
Ameren Illinois Company | Natural gas | Commodity Contract | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 9 | 3
Derivative Liability | 17 | 28
Ameren Illinois Company | Natural gas | Commodity Contract | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Assets | 5 | 3
Derivative Liability | 3 | 6
Ameren Illinois Company | Power | Commodity Contract |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Liability | 67 | 53
Ameren Illinois Company | Power | Commodity Contract | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Liability | 0 | 0
Ameren Illinois Company | Power | Commodity Contract | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Liability | 0 | 0
Ameren Illinois Company | Power | Commodity Contract | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative Liability | $ 67 | $ 53

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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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