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Fair Value of Financial Assets and Liabilities - Fair Value Inputs Assets Quantitative Information (Details) - Fair Value, Inputs, Level 3 [Member] - Derivative [Member] - USD ($) | Sep. 30, 2024 | Dec. 31, 2023
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Derivatives, Fair Value [Line Items] |  |
Derivative Liability, Fair Value, Amount Not Offset Against Collateral | $ (165,000,000) | $ (133,000,000)
Discounted Cash Flow [Member] | Minimum [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Inputs Forward Power Price | 22.68 | 30.27
Discounted Cash Flow [Member] | Maximum [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Inputs Forward Power Price | 55.35 | 73.71
Discounted Cash Flow [Member] | Arithmetic Average [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Inputs Forward Power Price | 36.45 | 43.35
Commonwealth Edison Co |  |
Derivatives, Fair Value [Line Items] |  |
Derivative Liability, Fair Value, Amount Not Offset Against Collateral | $ (165,000,000) | $ (133,000,000)
Commonwealth Edison Co | Discounted Cash Flow [Member] | Minimum [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Inputs Forward Power Price | 22.68 | 30.27
Commonwealth Edison Co | Discounted Cash Flow [Member] | Maximum [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Inputs Forward Power Price | 55.35 | 73.71
Commonwealth Edison Co | Discounted Cash Flow [Member] | Arithmetic Average [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Inputs Forward Power Price | 36.45 | 43.35

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- Definition Fair value, after offset of derivative asset, of financial liability or 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, elected not to be and before offset against a right to receive collateral under a master netting arrangement. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 55 -Paragraph 9 -SubTopic 20 -Topic 210 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483444/210-20-55-9 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -SubTopic 20 -Topic 210 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483466/210-20-50-3 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 55 -Paragraph 10 -SubTopic 20 -Topic 210 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483444/210-20-55-10 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-8 + Details
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