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Fair Value Measurements - Schedule of Commodity Derivatives (Details) $ in Millions | Mar. 31, 2020 USD ($) $ / MWh $ / kW-month | Dec. 31, 2019 USD ($)
--- | --- | ---
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | $ 506 | $ 550
CECONY |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | 453 | 498
Level 3 |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | 2 | 2
Level 3 | CECONY |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | 1 | $ 1
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 | 0.10 |
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 | 8.75 |
Level 3 | Electricity | Forward capacity prices | CECONY |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | $ (7) |
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 | 0.36 |
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 | 8.75 |
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 | (2.40) |
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 | 3.50 |
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 | 0.13 |
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 | 2.10 |
Level 3 | Commodity |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | $ (13) |
Level 3 | Commodity | CECONY |  |
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] |  |
Fair Value of commodity derivatives | $ (6) |

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