Derivative Instruments and Hedging Activities - Schedule of Fair Values of Commodity Derivatives Including Offsetting of Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/ (Liabilities)	$ 231	$ (105)
Gross Amounts Offset	(58)	3
Net Amounts of Assets/ (Liabilities)	173	(102)
CECONY
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/ (Liabilities)	214	(92)
Gross Amounts Offset	(56)	2
Net Amounts of Assets/ (Liabilities)	158	(90)
Current
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(75)	(92)
Gross Amounts Offset	45	44
Net Amounts of Assets/ (Liabilities)	(30)	(48)
Current | CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(70)	(84)
Gross Amounts Offset	43	42
Net Amounts of Assets/ (Liabilities)	(27)	(42)
Noncurrent
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(18)	(108)
Gross Amounts Offset	10	12
Net Amounts of Assets/ (Liabilities)	(8)	(96)
Noncurrent | CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(14)	(95)
Gross Amounts Offset	8	11
Net Amounts of Assets/ (Liabilities)	(6)	(84)
Total fair value of derivative liabilities
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(93)	(200)
Gross Amounts Offset	55	56
Net Amounts of Assets/ (Liabilities)	(38)	(144)
Net fair value derivative assets/(liabilities)
Margin deposit liability	(16)	4
Total fair value of derivative liabilities | CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(84)	(179)
Gross Amounts Offset	51	53
Net Amounts of Assets/ (Liabilities)	(33)	(126)
Net fair value derivative assets/(liabilities)
Margin deposit liability	(14)	2
Current
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	175	56
Gross Amounts Offset	(90)	(41)
Net Amounts of Assets/ (Liabilities)	85	15
Current | CECONY
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	162	51
Gross Amounts Offset	(88)	(40)
Net Amounts of Assets/ (Liabilities)	74	11
Noncurrent
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	149	39
Gross Amounts Offset	(23)	(12)
Net Amounts of Assets/ (Liabilities)	126	27
Noncurrent | CECONY
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	136	36
Gross Amounts Offset	(19)	(11)
Net Amounts of Assets/ (Liabilities)	117	25
Total fair value of derivative assets
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	324	95
Gross Amounts Offset	(113)	(53)
Net Amounts of Assets/ (Liabilities)	211	42
Net fair value derivative assets/(liabilities)
Margin deposit asset	1	0
Total fair value of derivative assets | CECONY
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	298	87
Gross Amounts Offset	(107)	(51)
Net Amounts of Assets/ (Liabilities)	191	36
Net fair value derivative assets/(liabilities)
Margin deposit asset	$ 0	$ 0