Fair Value Measurements - Schedule of Commodity Derivatives (Details) $ in Millions	Sep. 30, 2022 USD ($) $ / kW-month $ / MWh $ / Dt	Dec. 31, 2021 USD ($)
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives	$ 1,037	$ 832
CECONY | Subsidiaries
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives	836	728
Level 3
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives	37	17
Level 3 | CECONY | Subsidiaries
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives	9	$ 1
Level 3 | Electricity | Forward energy prices
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives	$ 17
Level 3 | Electricity | Forward energy prices | Minimum
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / MWh	22.25
Level 3 | Electricity | Forward energy prices | Maximum
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / MWh	172.80
Level 3 | Electricity | Forward energy prices | CECONY | Subsidiaries
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives	$ 4
Level 3 | Electricity | Forward energy prices | CECONY | Minimum | Subsidiaries
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / MWh	37.33
Level 3 | Electricity | Forward energy prices | CECONY | Maximum | Subsidiaries
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / MWh	172.80
Level 3 | Electricity | Forward capacity prices
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives	$ (4)
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	0.55
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	7.26
Level 3 | Electricity | Forward capacity prices | CECONY | Subsidiaries
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives	$ (6)
Level 3 | Electricity | Forward capacity prices | CECONY | Minimum | Subsidiaries
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / kW-month	1.10
Level 3 | Electricity | Forward capacity prices | CECONY | Maximum | Subsidiaries
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / kW-month	7.26
Level 3 | Natural Gas | Forward natural gas prices
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives	$ 0
Level 3 | Natural Gas | Forward natural gas prices | Minimum
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / Dt	3.75
Level 3 | Natural Gas | Forward natural gas prices | Maximum
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / Dt	21.37
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	$ 3
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	(12.89)
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	207.83
Level 3 | Commodity
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives	$ 16
Level 3 | Commodity | CECONY | Subsidiaries
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives	0
Level 3 | Transmission Congestion Contracts | Inter-zonal forward price curves adjusted for historical zonal losses | CECONY | Subsidiaries
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives	$ 2
Level 3 | Transmission Congestion Contracts | Inter-zonal forward price curves adjusted for historical zonal losses | CECONY | Minimum | Subsidiaries
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / MWh	1.03
Level 3 | Transmission Congestion Contracts | Inter-zonal forward price curves adjusted for historical zonal losses | CECONY | Maximum | Subsidiaries
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / MWh	5.51