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Supplemental Information (Allowance For Funds Used During Construction) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Allowance for Funds Used During Construction, Rate [Line Items] |  |  |
Allowance for equity funds used during construction | $ 76 | $ 54 | $ 43
Allowance for borrowed funds used during construction | 56 | 48 | 26
Allowance for equity funds used during construction | $ 132 | $ 102 | $ 69
Ameren Missouri |  |  |
Allowance for Funds Used During Construction, Rate [Line Items] |  |  |
Public Utilities, Allowance for Funds Used During Construction, Rate | 6.00% | 6.00% | 5.00%
Allowance for equity funds used during construction | $ 58 | $ 30 | $ 24
Allowance for borrowed funds used during construction | 39 | 27 | 13
Allowance for equity funds used during construction | $ 97 | $ 57 | $ 37
Ameren Illinois |  |  |
Allowance for Funds Used During Construction, Rate [Line Items] |  |  |
Public Utilities, Allowance for Funds Used During Construction, Rate | 6.00% | 6.00% | 5.00%
Allowance for equity funds used during construction | $ 17 | $ 19 | $ 18
Allowance for borrowed funds used during construction | 15 | 17 | 12
Allowance for equity funds used during construction | $ 32 | $ 36 | $ 30

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- Definition Total increase in earnings in the period representing the cost of equity (based on assumed rate of return) and/or borrowed funds (based on interest rate) used to finance construction of regulated assets, which is expected to be recovered through rate adjustments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Subparagraph (b) -SubTopic 10 -Topic 230 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-28 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section 25 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477468/980-360-25-1 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478742/980-340-50-3 + Details
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- Definition The component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 25 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478698/980-835-25-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479123/980-835-45-1 + Details
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- Definition Amount capitalized of allowance for funds used during construction. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 25 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478698/980-835-25-1 + Details
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- Definition Effective rate, including composite rate, of cost of financing additions to qualifying regulated assets, commonly called allowance for funds used during construction. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 25 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478698/980-835-25-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479123/980-835-45-1 + Details
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