Derivative Instruments and Hedging Activities - Fair Values of Commodity Derivatives Including Offsetting (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	$ 946	$ 832
Fair value of derivative liabilities
Net Amounts of Assets/ (Liabilities)	(171)	(236)
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/(Liabilities)	471	(8)
Gross Amounts Offset	(229)	(24)
Net Amounts of Assets/ (Liabilities)	242	(32)
Interest Rate Swap
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	56	4
Fair value of derivative liabilities
Net Amounts of Assets/ (Liabilities)	0	(57)
CECONY \| Subsidiaries
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	785	728
Fair value of derivative liabilities
Net Amounts of Assets/ (Liabilities)	(141)	(128)
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/(Liabilities)	368	25
Gross Amounts Offset	(235)	(26)
Net Amounts of Assets/ (Liabilities)	133	(1)
Clean Energy Businesses \| Interest Rate Swap
Net fair value derivative assets/(liabilities)
Notional amount	1,002	1,031
Total fair value of derivative assets, Noncurrent \| Interest Rate Swap
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	50	4
Total fair value of derivative liabilities
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(371)	(383)
Gross Amounts Offset	215	147
Net Amounts of Assets/ (Liabilities)	(156)	(236)
Net fair value derivative assets/(liabilities)
Margin deposits	16
Total fair value of derivative liabilities \| CECONY \| Subsidiaries
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(228)	(181)
Gross Amounts Offset	102	53
Net Amounts of Assets/ (Liabilities)	(126)	(128)
Net fair value derivative assets/(liabilities)
Margin deposits	14
Fair value of derivative liabilities, Current
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(280)	(289)
Gross Amounts Offset	186	137
Net Amounts of Assets/ (Liabilities)	(94)	(152)
Fair value of derivative liabilities, Current \| Interest Rate Swap
Fair value of derivative liabilities
Net Amounts of Assets/ (Liabilities)		(20)
Fair value of derivative liabilities, Current \| CECONY \| Subsidiaries
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(148)	(131)
Gross Amounts Offset	68	43
Net Amounts of Assets/ (Liabilities)	(80)	(88)
Fair value of derivative liabilities, Noncurrent
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(91)	(94)
Gross Amounts Offset	29	10
Net Amounts of Assets/ (Liabilities)	(62)	(84)
Fair value of derivative liabilities, Noncurrent \| Interest Rate Swap
Fair value of derivative liabilities
Net Amounts of Assets/ (Liabilities)		(38)
Fair value of derivative liabilities, Noncurrent \| CECONY \| Subsidiaries
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(80)	(50)
Gross Amounts Offset	34	10
Net Amounts of Assets/ (Liabilities)	(46)	(40)
Fair value of derivative assets, Current \| Interest Rate Swap
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	6
Fair value of derivative assets, Current
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	631	285
Gross Amounts Offset	(376)	(158)
Net Amounts of Assets/ (Liabilities)	255	127
Fair value of derivative assets, Current \| CECONY \| Subsidiaries
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	456	135
Gross Amounts Offset	(265)	(64)
Net Amounts of Assets/ (Liabilities)	191	71
Total fair value of derivative assets, Noncurrent
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	211	90
Gross Amounts Offset	(68)	(13)
Net Amounts of Assets/ (Liabilities)	143	77
Total fair value of derivative assets, Noncurrent \| CECONY \| Subsidiaries
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	140	71
Gross Amounts Offset	(72)	(15)
Net Amounts of Assets/ (Liabilities)	68	56
Total fair value of derivative assets
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	842	375
Gross Amounts Offset	(444)	(171)
Net Amounts of Assets/ (Liabilities)	398	204
Net fair value derivative assets/(liabilities)
Margin deposits	5	1
Total fair value of derivative assets \| CECONY \| Subsidiaries
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	596	206
Gross Amounts Offset	(337)	(79)
Net Amounts of Assets/ (Liabilities)	259	127
Net fair value derivative assets/(liabilities)
Margin deposits	$ 5	$ 0

Derivative Asset (Liability), Gross Amount Offset in Balance Sheet

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Offsetting Derivative Assets and Liabilities [Abstract]

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Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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Nominal or face amount used to calculate payment on derivative.

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The amount of cash or securities placed with a broker or counterparty as security for a trading or derivatives securities position which was partially obtained with funds provided by the broker dealer.

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