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Fair Value of Financial Assets and Liabilities - Fair Value Assets Liabilities Measured On Recurring Basis Unobservable Input Reconciliation (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023 | Dec. 31, 2023
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract] |  |  |  |  |
Mark-to-market derivative liabilities (current liabilities) | $ 25 |  | $ 25 |  | $ 74
Mark-to-market derivative liabilities (noncurrent liabilities) | 180 |  | 180 |  | 106
Fair Value, Inputs, Level 3 [Member] |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |  |
Beginning Balance | (116) | $ (91) | (90) | $ (44) |
Total realized / unrealized gains (losses) |  |  |  |  |
Included in net income | 0 | 0 | 1 | 2 |
Included in regulatory assets/liabilities | (26) | (1) | (32) | (50) |
Purchases, sales, issuances and settlements |  |  |  |  |
Settlements | (1) |  | (22) |  |
Ending Balance | (143) | (92) | (143) | (92) |
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss) | 0 | 0 | 2 | 2 |
Commonwealth Edison Co |  |  |  |  |
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract] |  |  |  |  |
Mark-to-market derivative liabilities (current liabilities) | 25 |  | 25 |  | 27
Mark-to-market derivative liabilities (noncurrent liabilities) | 140 |  | 140 |  | 106
Commonwealth Edison Co | Fair Value, Recurring [Member] |  |  |  |  |
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract] |  |  |  |  |
Mark-to-market derivative liabilities (current liabilities) | 25 |  | 25 |  | 27
Mark-to-market derivative liabilities (noncurrent liabilities) | 140 |  | 140 |  | $ 106
Other current assets | 0 |  | 0 |  |
Other deferred debits (noncurrent assets) | 0 |  | 0 |  |
Commonwealth Edison Co | Derivative [Member] | Interest Rate Swap |  |  |  |  |
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract] |  |  |  |  |
Realized Investment Gains (Losses) | 5 | 4 | 28 | 23 |
Commonwealth Edison Co | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |  |
Beginning Balance | (139) | (133) | (133) | (84) |
Total realized / unrealized gains (losses) |  |  |  |  |
Included in net income | 0 | 0 | 0 | 0 |
Included in regulatory assets/liabilities | (26) | (1) | (32) | (50) |
Purchases, sales, issuances and settlements |  |  |  |  |
Settlements | 0 |  | 0 |  |
Ending Balance | (165) | (134) | (165) | (134) |
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss) | 0 | 0 | 0 | 0 |
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract] |  |  |  |  |
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Period Increase (Decrease) | (31) | (5) | (60) | (73) |
Pepco Holdings LLC | Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member] |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |  |
Beginning Balance | 22 | 42 | 41 | 40 |
Total realized / unrealized gains (losses) |  |  |  |  |
Included in net income | 0 | (2) | 2 | 0 |
Included in regulatory assets/liabilities | 0 | 0 | 0 | 0 |
Purchases, sales, issuances and settlements |  |  |  |  |
Settlements | (1) |  | (22) |  |
Ending Balance | 21 | 40 | 21 | 40 |
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss) | 0 | (2) | 2 | 0 |
Potomac Electric Power Company | Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member] |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |  |
Beginning Balance | 22 | 42 | 41 | 40 |
Total realized / unrealized gains (losses) |  |  |  |  |
Included in net income | 0 | (2) | 2 | 0 |
Included in regulatory assets/liabilities | 0 | 0 | 0 | 0 |
Purchases, sales, issuances and settlements |  |  |  |  |
Settlements | (1) |  | (22) |  |
Ending Balance | 21 | 40 | 21 | 40 |
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss) | $ 0 | $ (2) | $ 2 | $ 0 |

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