Fair Value Measurements - Schedule of Commodity Derivatives (Details) - Level 3 $ in Millions	Mar. 31, 2026 USD ($) $ / kW-month $ / MWh
Electricity | Forward capacity prices | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives | $	$ 7
Electricity | Forward capacity prices | Minimum | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / kW-month	8.37
Electricity | Forward capacity prices | Maximum | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / kW-month	1.36
Electricity | Forward capacity prices | Average Market Price | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / kW-month	4.68
Electricity | Forward capacity prices | CECONY | Subsidiaries | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives | $	$ 2
Electricity | Forward capacity prices | CECONY | Minimum | Subsidiaries | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / kW-month	1.36
Electricity | Forward capacity prices | CECONY | Maximum | Subsidiaries | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / kW-month	8.37
Electricity | Forward capacity prices | CECONY | Average Market Price | Subsidiaries | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / kW-month	4.64
Transmission Congestion Contracts | Inter-zonal forward price curves adjusted for historical zonal losses | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives | $	$ 1
Transmission Congestion Contracts | Inter-zonal forward price curves adjusted for historical zonal losses | Minimum | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / MWh	(0.03)
Transmission Congestion Contracts | Inter-zonal forward price curves adjusted for historical zonal losses | Maximum | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / MWh	1.83
Transmission Congestion Contracts | Inter-zonal forward price curves adjusted for historical zonal losses | Average Market Price | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / MWh	0.72
Transmission Congestion Contracts | Inter-zonal forward price curves adjusted for historical zonal losses | CECONY | Subsidiaries | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives | $	$ 1
Transmission Congestion Contracts | Inter-zonal forward price curves adjusted for historical zonal losses | CECONY | Minimum | Subsidiaries | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / MWh	(0.03)
Transmission Congestion Contracts | Inter-zonal forward price curves adjusted for historical zonal losses | CECONY | Maximum | Subsidiaries | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / MWh	1.83
Transmission Congestion Contracts | Inter-zonal forward price curves adjusted for historical zonal losses | CECONY | Average Market Price | Subsidiaries | Valuation Technique, Discounted Cash Flow
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per unit) | $ / MWh	0.72
Commodity
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives | $	$ 8
Commodity | CECONY | Subsidiaries
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives | $	$ 3