Derivative Instruments and Hedging Activities - Fair Values of Commodity Derivatives Including Offsetting (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	$ 1,042	$ 832
Fair value of derivative liabilities
Net Amounts of Assets/ (Liabilities)	(210)	(236)
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/(Liabilities)	367	(8)
Gross Amounts Offset	(132)	(24)
Net Amounts of Assets/ (Liabilities)	235	(32)
Margin deposits	1	1
Interest Rate Swap
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	24	4
Fair value of derivative liabilities
Net Amounts of Assets/ (Liabilities)	(13)	(57)
CECONY \| Subsidiaries
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	888	728
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/(Liabilities)	310	25
Gross Amounts Offset	(154)	(26)
Net Amounts of Assets/ (Liabilities)	156	(1)
Clean Energy Businesses \| Interest Rate Swap
Net fair value derivative assets/(liabilities)
Notional amount	1,014	1,031
Total fair value of derivative assets, Noncurrent \| Interest Rate Swap
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	24	4
Fair value of derivative liabilities, Current
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(330)	(289)
Gross Amounts Offset	196	137
Net Amounts of Assets/ (Liabilities)	(134)	(152)
Fair value of derivative liabilities, Current \| Interest Rate Swap
Fair value of derivative liabilities
Net Amounts of Assets/ (Liabilities)	(9)	(20)
Fair value of derivative liabilities, Current \| CECONY \| Subsidiaries
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(215)	(131)
Gross Amounts Offset	119	43
Net Amounts of Assets/ (Liabilities)	(96)	(88)
Fair value of derivative liabilities, Noncurrent
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(94)	(94)
Gross Amounts Offset	18	10
Net Amounts of Assets/ (Liabilities)	(76)	(84)
Fair value of derivative liabilities, Noncurrent \| Interest Rate Swap
Fair value of derivative liabilities
Net Amounts of Assets/ (Liabilities)	(4)	(38)
Fair value of derivative liabilities, Noncurrent \| CECONY \| Subsidiaries
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(82)	(50)
Gross Amounts Offset	19	10
Net Amounts of Assets/ (Liabilities)	(63)	(40)
Total fair value of derivative liabilities
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(424)	(383)
Gross Amounts Offset	214	147
Net Amounts of Assets/ (Liabilities)	(210)	(236)
Total fair value of derivative liabilities \| CECONY \| Subsidiaries
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(297)	(181)
Gross Amounts Offset	138	53
Net Amounts of Assets/ (Liabilities)	(159)	(128)
Fair value of derivative assets, Current
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	637	285
Gross Amounts Offset	(328)	(158)
Net Amounts of Assets/ (Liabilities)	309	127
Fair value of derivative assets, Current \| CECONY \| Subsidiaries
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	497	135
Gross Amounts Offset	(270)	(64)
Net Amounts of Assets/ (Liabilities)	227	71
Total fair value of derivative assets, Noncurrent
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	154	90
Gross Amounts Offset	(18)	(13)
Net Amounts of Assets/ (Liabilities)	136	77
Total fair value of derivative assets, Noncurrent \| CECONY \| Subsidiaries
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	110	71
Gross Amounts Offset	(22)	(15)
Net Amounts of Assets/ (Liabilities)	88	56
Total fair value of derivative assets
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	791	375
Gross Amounts Offset	(346)	(171)
Net Amounts of Assets/ (Liabilities)	445	204
Total fair value of derivative assets \| CECONY \| Subsidiaries
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	607	206
Gross Amounts Offset	(292)	(79)
Net Amounts of Assets/ (Liabilities)	$ 315	$ 127

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Offsetting Derivative Assets and Liabilities [Abstract]

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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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