Fair Value Measurements - Schedule of Reconciliation of Assets and Liabilities Measured at Level 3 Fair Value (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] | ||||
| Beginning balance | $ 8 | $ (13) | $ (5) | $ (15) |
| Included in earnings | 3 | (1) | 0 | (3) |
| Included in regulatory assets and liabilities | (4) | (4) | 10 | (1) |
| Settlements | (3) | 1 | 0 | 2 |
| Transfer out of level 3 | 0 | 0 | (1) | 0 |
| Ending balance | 4 | (17) | 4 | (17) |
| CECONY | Subsidiaries | ||||
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] | ||||
| Beginning balance | 3 | (5) | (3) | (6) |
| Included in earnings | 1 | 0 | 0 | 0 |
| Included in regulatory assets and liabilities | 1 | (3) | 8 | (2) |
| Settlements | (1) | 0 | 0 | 0 |
| Transfer out of level 3 | 0 | 0 | (1) | 0 |
| Ending balance | $ 4 | $ (8) | $ 4 | $ (8) |