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Fair Value Measurements - Schedule of Commodity Derivatives (Details) $ in Millions | Mar. 31, 2021 USD ($) $ / kW-month $ / MWh | Dec. 31, 2020 USD ($)
--- | --- | ---
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | $ 697 | $ 675
CECONY |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | 570 | 550
Level 3 |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | 6 | 4
Level 3 | CECONY |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | 1 | $ 0
Level 3 | Electricity | Forward energy prices |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | $ 1 |
Level 3 | Electricity | Forward energy prices | Minimum |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Unobservable Inputs Range (dollar per unit) | $ / MWh | 14.25 |
Level 3 | Electricity | Forward energy prices | Maximum |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Unobservable Inputs Range (dollar per unit) | $ / MWh | 63.00 |
Level 3 | Electricity | Forward capacity prices |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | $ (14) |
Level 3 | Electricity | Forward capacity prices | Minimum |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Unobservable Inputs Range (dollar per unit) | $ / kW-month | 0.26 |
Level 3 | Electricity | Forward capacity prices | Maximum |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Unobservable Inputs Range (dollar per unit) | $ / kW-month | 6.26 |
Level 3 | Electricity | Forward capacity prices | CECONY |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | $ (8) |
Level 3 | Electricity | Forward capacity prices | CECONY | Minimum |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Unobservable Inputs Range (dollar per unit) | $ / kW-month | 1.08 |
Level 3 | Electricity | Forward capacity prices | CECONY | Maximum |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Unobservable Inputs Range (dollar per unit) | $ / kW-month | 6.26 |
Level 3 | Transmission Congestion Contracts/Financial Transmission Rights | Inter-zonal forward price curves adjusted for historical zonal losses |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | $ 1 |
Level 3 | Transmission Congestion Contracts/Financial Transmission Rights | Inter-zonal forward price curves adjusted for historical zonal losses | Minimum |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Unobservable Inputs Range (dollar per unit) | $ / MWh | (3.75) |
Level 3 | Transmission Congestion Contracts/Financial Transmission Rights | Inter-zonal forward price curves adjusted for historical zonal losses | Maximum |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Unobservable Inputs Range (dollar per unit) | $ / MWh | 8.07 |
Level 3 | Transmission Congestion Contracts | Inter-zonal forward price curves adjusted for historical zonal losses | CECONY |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | $ 1 |
Level 3 | Transmission Congestion Contracts | Inter-zonal forward price curves adjusted for historical zonal losses | CECONY | Minimum |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Unobservable Inputs Range (dollar per unit) | $ / MWh | 0.35 |
Level 3 | Transmission Congestion Contracts | Inter-zonal forward price curves adjusted for historical zonal losses | CECONY | Maximum |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Unobservable Inputs Range (dollar per unit) | $ / MWh | 2.54 |
Level 3 | Commodity |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | $ (12) |
Level 3 | Commodity | CECONY |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | $ (7) |

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