Derivative Instruments and Hedging Activities - Fair Values of Commodity Derivatives Including Offsetting (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	$ 783	$ 723
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/(Liabilities)	(89)	(224)
Gross Amounts Offset	18	18
Net Amounts of Assets/ (Liabilities)	(71)	(206)
CECONY | Subsidiaries
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	753	699
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/(Liabilities)	(78)	(202)
Gross Amounts Offset	15	17
Net Amounts of Assets/ (Liabilities)	(63)	(185)
Current
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(164)	(230)
Gross Amounts Offset	58	52
Net Amounts of Assets/ (Liabilities)	(106)	(178)
Current | CECONY | Subsidiaries
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(156)	(217)
Gross Amounts Offset	55	48
Net Amounts of Assets/ (Liabilities)	(101)	(169)
Noncurrent
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(123)	(154)
Gross Amounts Offset	29	33
Net Amounts of Assets/ (Liabilities)	(94)	(121)
Noncurrent | CECONY | Subsidiaries
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(112)	(139)
Gross Amounts Offset	27	31
Net Amounts of Assets/ (Liabilities)	(85)	(108)
Total fair value of derivative liabilities
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(287)	(384)
Gross Amounts Offset	87	85
Net Amounts of Assets/ (Liabilities)	(200)	(299)
Net fair value derivative assets/(liabilities)
Margin deposit liability	(7)	(15)
Total fair value of derivative liabilities | CECONY
Net fair value derivative assets/(liabilities)
Margin deposit liability		(10)
Total fair value of derivative liabilities | CECONY | Subsidiaries
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/(Liabilities)	(268)	(356)
Gross Amounts Offset	82	79
Net Amounts of Assets/ (Liabilities)	(186)	(277)
Net fair value derivative assets/(liabilities)
Margin deposit liability	(2)
Current
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	127	83
Gross Amounts Offset	(46)	(38)
Net Amounts of Assets/ (Liabilities)	81	45
Current | CECONY | Subsidiaries
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	121	78
Gross Amounts Offset	(45)	(35)
Net Amounts of Assets/ (Liabilities)	76	43
Noncurrent
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	71	77
Gross Amounts Offset	(23)	(29)
Net Amounts of Assets/ (Liabilities)	48	48
Noncurrent | CECONY | Subsidiaries
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	69	76
Gross Amounts Offset	(22)	(27)
Net Amounts of Assets/ (Liabilities)	47	49
Total fair value of derivative assets
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	198	160
Gross Amounts Offset	(69)	(67)
Net Amounts of Assets/ (Liabilities)	129	93
Net fair value derivative assets/(liabilities)
Margin deposits assets	7	7
Total fair value of derivative assets | CECONY
Net fair value derivative assets/(liabilities)
Margin deposits assets		6
Total fair value of derivative assets | CECONY | Subsidiaries
Fair value of derivative assets
Gross Amounts of Recognized Assets/(Liabilities)	190	154
Gross Amounts Offset	(67)	(62)
Net Amounts of Assets/ (Liabilities)	123	$ 92
Net fair value derivative assets/(liabilities)
Margin deposits assets	$ 6