Derivative Instruments and Hedging Activities - Fair Values of Commodity Derivatives Including Offsetting of Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/ (Liabilities)	$ (224)	$ 466
Gross Amounts Offset	18	(237)
Net Amounts of Assets/ (Liabilities)	(206)	229
CECONY
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/ (Liabilities)	(202)	294
Gross Amounts Offset	17	(214)
Net Amounts of Assets/ (Liabilities)	(185)	80
Clean Energy Businesses | Interest Rate Swap
Net fair value derivative assets/(liabilities)
Notional amount		982
Fair Value of Derivative Liabilities, Current
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(230)	(198)
Gross Amounts Offset	52	166
Net Amounts of Assets/ (Liabilities)	(178)	(32)
Fair Value of Derivative Liabilities, Current | CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(217)	(189)
Gross Amounts Offset	48	160
Net Amounts of Assets/ (Liabilities)	(169)	(29)
Fair Value of Derivative Liabilities, Non-current
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(154)	(49)
Gross Amounts Offset	33	36
Net Amounts of Assets/ (Liabilities)	(121)	(13)
Fair Value of Derivative Liabilities, Non-current | CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(139)	(43)
Gross Amounts Offset	31	34
Net Amounts of Assets/ (Liabilities)	(108)	(9)
Fair Value of Derivative Liabilities, Held and Used Liabilities
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(384)	(247)
Gross Amounts Offset	85	202
Net Amounts of Assets/ (Liabilities)	(299)	(45)
Fair Value of Derivative Liabilities, Held for Sale Liabilities, Current
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	0	(31)
Gross Amounts Offset	0	6
Net Amounts of Assets/ (Liabilities)	0	(25)
Fair Value of Derivative Liabilities, Held for Sale Liabilities, Non-Current
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	0	(3)
Gross Amounts Offset	0	(8)
Net Amounts of Assets/ (Liabilities)	0	(11)
Fair Value of Derivative Liabilities
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(384)	(281)
Gross Amounts Offset	85	200
Net Amounts of Assets/ (Liabilities)	(299)	(81)
Net fair value derivative assets/(liabilities)
Margin deposit liability	(15)	(10)
Fair Value of Derivative Liabilities | CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(356)	(232)
Gross Amounts Offset	79	194
Net Amounts of Assets/ (Liabilities)	(277)	(38)
Net fair value derivative assets/(liabilities)
Margin deposit liability	(10)	(6)
Fair Value of Derivative Assets, Current
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	83	378
Gross Amounts Offset	(38)	(332)
Net Amounts of Assets/ (Liabilities)	45	46
Fair Value of Derivative Assets, Current | Interest Rate Swap
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)		31
Fair Value of Derivative Assets, Current | CECONY
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	78	350
Gross Amounts Offset	(35)	(312)
Net Amounts of Assets/ (Liabilities)	43	38
Fair Value of Derivative Assets, Non-current
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	77	193
Gross Amounts Offset	(29)	(108)
Net Amounts of Assets/ (Liabilities)	48	85
Fair Value of Derivative Assets, Non-current | Interest Rate Swap
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)		75
Fair Value of Derivative Assets, Non-current | CECONY
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	76	176
Gross Amounts Offset	(27)	(96)
Net Amounts of Assets/ (Liabilities)	49	80
Fair Value of Derivative Assets, Held and Used Assets
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	160	571
Gross Amounts Offset	(67)	(440)
Net Amounts of Assets/ (Liabilities)	93	131
Fair Value of Derivative Assets, Held-For-Sale Assets, Current
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	0	93
Gross Amounts Offset	0	(8)
Net Amounts of Assets/ (Liabilities)	0	85
Fair Value of Derivative Assets, Held-For Sale Assets, Non-Current
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	0	83
Gross Amounts Offset	0	11
Net Amounts of Assets/ (Liabilities)	0	94
Fair Value of Derivative Assets
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	160	747
Gross Amounts Offset	(67)	(437)
Net Amounts of Assets/ (Liabilities)	93	310
Net fair value derivative assets/(liabilities)
Margin deposits	7	13
Fair Value of Derivative Assets | CECONY
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	154	526
Gross Amounts Offset	(62)	(408)
Net Amounts of Assets/ (Liabilities)	92	$ 118
Net fair value derivative assets/(liabilities)
Margin deposits	$ 6