Derivative Instruments and Hedging Activities - Schedule of Fair Values of Commodity Derivatives Including Offsetting (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Fair value of derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	$ 270	$ 231
Gross Amounts Offset	(30)	(58)
Net Amounts of Assets/ (Liabilities)	240	173
CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	248	214
Gross Amounts Offset	(28)	(56)
Net Amounts of Assets/ (Liabilities)	220	158
Current
Fair value of derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(61)	(75)
Gross Amounts Offset	52	45
Net Amounts of Assets/ (Liabilities)	(9)	(30)
Current | CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(57)	(70)
Gross Amounts Offset	50	43
Net Amounts of Assets/ (Liabilities)	(7)	(27)
Noncurrent
Fair value of derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(27)	(18)
Gross Amounts Offset	21	10
Net Amounts of Assets/ (Liabilities)	(6)	(8)
Noncurrent | CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(25)	(14)
Gross Amounts Offset	20	8
Net Amounts of Assets/ (Liabilities)	(5)	(6)
Total fair value of derivative liabilities
Fair value of derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(88)	(93)
Gross Amounts Offset	73	55
Net Amounts of Assets/ (Liabilities)	(15)	(38)
Fair value of derivative liabilities
Margin deposit liability	1	(16)
Total fair value of derivative liabilities | CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(82)	(84)
Gross Amounts Offset	70	51
Net Amounts of Assets/ (Liabilities)	(12)	(33)
Fair value of derivative liabilities
Margin deposit liability	0	(14)
Current
Fair value of derivative assets
Gross Amounts of Recognized Assets (Liabilities)	259	175
Gross Amounts Offset	(78)	(90)
Net Amounts of Assets (Liabilities)	181	85
Current | CECONY
Fair value of derivative assets
Gross Amounts of Recognized Assets (Liabilities)	239	162
Gross Amounts Offset	(76)	(88)
Net Amounts of Assets (Liabilities)	163	74
Noncurrent
Fair value of derivative assets
Gross Amounts of Recognized Assets (Liabilities)	99	149
Gross Amounts Offset	(25)	(23)
Net Amounts of Assets (Liabilities)	74	126
Noncurrent | CECONY
Fair value of derivative assets
Gross Amounts of Recognized Assets (Liabilities)	91	136
Gross Amounts Offset	(22)	(19)
Net Amounts of Assets (Liabilities)	69	117
Total fair value of derivative assets
Fair value of derivative assets
Gross Amounts of Recognized Assets (Liabilities)	358	324
Gross Amounts Offset	(103)	(113)
Net Amounts of Assets (Liabilities)	255	211
Fair value of derivative liabilities
Margin Deposit Asset	1	1
Total fair value of derivative assets | CECONY
Fair value of derivative assets
Gross Amounts of Recognized Assets (Liabilities)	330	298
Gross Amounts Offset	(98)	(107)
Net Amounts of Assets (Liabilities)	232	191
Fair value of derivative liabilities
Margin Deposit Asset	$ 1	$ 0