Derivative Instruments and Hedging Activities - Fair Values of Commodity Derivatives Including Offsetting (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	$ 671	$ 874
Fair value of derivative liabilities
Net Amounts of Assets/ (Liabilities)	(155)	(90)
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/(Liabilities)	(65)	466
Gross Amounts Offset	4	(237)
Net Amounts of Assets/ (Liabilities)	(61)	229
Interest Rate Swap
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	0	106
CECONY | Subsidiaries
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	645	663
Fair value of derivative liabilities
Net Amounts of Assets/ (Liabilities)	(139)	(44)
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/(Liabilities)	(60)	294
Gross Amounts Offset	5	(214)
Net Amounts of Assets/ (Liabilities)	(55)	80
Clean Energy Businesses | Interest Rate Swap
Net fair value derivative assets/(liabilities)
Notional amount		982
Current
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(135)	(198)
Gross Amounts Offset	64	166
Net Amounts of Assets/ (Liabilities)	(71)	(32)
Current | Interest Rate Swap
Fair value of derivative liabilities
Net Amounts of Assets/ (Liabilities)		31
Current | CECONY | Subsidiaries
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(129)	(189)
Gross Amounts Offset	61	160
Net Amounts of Assets/ (Liabilities)	(68)	(29)
Noncurrent
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(108)	(49)
Gross Amounts Offset	40	36
Net Amounts of Assets/ (Liabilities)	(68)	(13)
Noncurrent | CECONY | Subsidiaries
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(98)	(43)
Gross Amounts Offset	38	34
Net Amounts of Assets/ (Liabilities)	(60)	(9)
Total fair value of derivative liabilities held and used
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(243)	(247)
Gross Amounts Offset	104	202
Net Amounts of Assets/ (Liabilities)	(139)	(45)
Current - liabilities held for sale
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)
Noncurrent - liabilities held for sale
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)
Total fair value of derivative liabilities
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(243)	(281)
Gross Amounts Offset	104	200
Net Amounts of Assets/ (Liabilities)	(139)	(81)
Net fair value derivative assets/(liabilities)
Margin deposit liability	(15)	(10)
Total fair value of derivative liabilities | CECONY
Net fair value derivative assets/(liabilities)
Margin deposit liability		(6)
Total fair value of derivative liabilities | CECONY | Subsidiaries
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(227)	(232)
Gross Amounts Offset	99	194
Net Amounts of Assets/ (Liabilities)	(128)	(38)
Net fair value derivative assets/(liabilities)
Margin deposit liability	(11)
Noncurrent | Interest Rate Swap
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)		75
Current
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	115	378
Gross Amounts Offset	(63)	(332)
Net Amounts of Assets/ (Liabilities)	52	46
Current | CECONY | Subsidiaries
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	107	350
Gross Amounts Offset	(60)	(312)
Net Amounts of Assets/ (Liabilities)	47	38
Noncurrent
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	63	193
Gross Amounts Offset	(37)	(108)
Net Amounts of Assets/ (Liabilities)	26	85
Noncurrent | CECONY | Subsidiaries
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	60	176
Gross Amounts Offset	(34)	(96)
Net Amounts of Assets/ (Liabilities)	26	80
Total fair value of derivative assets held and used
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	178	571
Gross Amounts Offset	(100)	(440)
Net Amounts of Assets/ (Liabilities)	78	131
Current - assets held for sale
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
Noncurrent - assets held for sale
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
Total fair value of derivative assets
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	178	747
Gross Amounts Offset	(100)	(437)
Net Amounts of Assets/ (Liabilities)	78	310
Net fair value derivative assets/(liabilities)
Margin deposits assets	10	13
Total fair value of derivative assets | CECONY
Net fair value derivative assets/(liabilities)
Margin deposits assets		13
Total fair value of derivative assets | CECONY | Subsidiaries
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	167	526
Gross Amounts Offset	(94)	(408)
Net Amounts of Assets/ (Liabilities)	73	$ 118
Net fair value derivative assets/(liabilities)
Margin deposits assets	$ 9