Derivative Instruments and Hedging Activities - Fair Values of Commodity Derivatives Including Offsetting of Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/ (Liabilities)	$ (105)	$ (224)
Gross Amounts Offset	3	18
Net Amounts of Assets/ (Liabilities)	(102)	(206)
CECONY
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/ (Liabilities)	(92)	(202)
Gross Amounts Offset	2	17
Net Amounts of Assets/ (Liabilities)	(90)	(185)
Fair Value of Derivative Liabilities, Current
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(92)	(230)
Gross Amounts Offset	44	52
Net Amounts of Assets/ (Liabilities)	(48)	(178)
Fair Value of Derivative Liabilities, Current | CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(84)	(217)
Gross Amounts Offset	42	48
Net Amounts of Assets/ (Liabilities)	(42)	(169)
Fair Value of Derivative Liabilities, Non-current
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(108)	(154)
Gross Amounts Offset	12	33
Net Amounts of Assets/ (Liabilities)	(96)	(121)
Fair Value of Derivative Liabilities, Non-current | CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(95)	(139)
Gross Amounts Offset	11	31
Net Amounts of Assets/ (Liabilities)	(84)	(108)
Fair Value of Derivative Liabilities
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(200)	(384)
Gross Amounts Offset	56	85
Net Amounts of Assets/ (Liabilities)	(144)	(299)
Net fair value derivative assets/(liabilities)
Margin deposit liability	(4)	(15)
Fair Value of Derivative Liabilities | CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(179)	(356)
Gross Amounts Offset	53	79
Net Amounts of Assets/ (Liabilities)	(126)	(277)
Net fair value derivative assets/(liabilities)
Margin deposit liability	(2)	(10)
Fair Value of Derivative Assets, Current
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	56	83
Gross Amounts Offset	(41)	(38)
Net Amounts of Assets/ (Liabilities)	15	45
Fair Value of Derivative Assets, Current | CECONY
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	51	78
Gross Amounts Offset	(40)	(35)
Net Amounts of Assets/ (Liabilities)	11	43
Fair Value of Derivative Assets, Non-current
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	39	77
Gross Amounts Offset	(12)	(29)
Net Amounts of Assets/ (Liabilities)	27	48
Fair Value of Derivative Assets, Non-current | CECONY
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	36	76
Gross Amounts Offset	(11)	(27)
Net Amounts of Assets/ (Liabilities)	25	49
Fair Value of Derivative Assets
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	95	160
Gross Amounts Offset	(53)	(67)
Net Amounts of Assets/ (Liabilities)	42	93
Net fair value derivative assets/(liabilities)
Margin deposits		7
Fair Value of Derivative Assets | CECONY
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	87	154
Gross Amounts Offset	(51)	(62)
Net Amounts of Assets/ (Liabilities)	$ 36	92
Net fair value derivative assets/(liabilities)
Margin deposits		$ 6