Derivative Instruments and Hedging Activities - Fair Values of Commodity Derivatives Including Offsetting (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Fair value of derivative assets
Net Amounts of Assets (Liabilities)	$ 727	$ 723
Net fair value derivative assets (liabilities)
Gross Amounts of Recognized Assets (Liabilities)	(103)	(224)
Gross Amounts Offset	9	18
Net Amounts of Assets/ (Liabilities)	(94)	(206)
CECONY | Subsidiaries
Fair value of derivative assets
Net Amounts of Assets (Liabilities)	698	699
Net fair value derivative assets (liabilities)
Gross Amounts of Recognized Assets (Liabilities)	(94)	(202)
Gross Amounts Offset	9	17
Net Amounts of Assets/ (Liabilities)	(85)	(185)
Current
Fair value of derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(131)	(230)
Gross Amounts Offset	55	52
Net Amounts of Assets/ (Liabilities)	(76)	(178)
Current | CECONY | Subsidiaries
Fair value of derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(122)	(217)
Gross Amounts Offset	53	48
Net Amounts of Assets/ (Liabilities)	(69)	(169)
Noncurrent
Fair value of derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(107)	(154)
Gross Amounts Offset	33	33
Net Amounts of Assets/ (Liabilities)	(74)	(121)
Noncurrent | CECONY | Subsidiaries
Fair value of derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(97)	(139)
Gross Amounts Offset	32	31
Net Amounts of Assets/ (Liabilities)	(65)	(108)
Total fair value of derivative liabilities
Fair value of derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(238)	(384)
Gross Amounts Offset	88	85
Net Amounts of Assets/ (Liabilities)	(150)	(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)	(219)	(356)
Gross Amounts Offset	85	79
Net Amounts of Assets/ (Liabilities)	(134)	(277)
Net fair value derivative assets (liabilities)
Margin deposit liability	(2)
Current
Fair value of derivative assets
Gross Amounts of Recognized Assets (Liabilities)	84	83
Gross Amounts Offset	(49)	(38)
Net Amounts of Assets (Liabilities)	35	45
Current | CECONY | Subsidiaries
Fair value of derivative assets
Gross Amounts of Recognized Assets (Liabilities)	78	78
Gross Amounts Offset	(48)	(35)
Net Amounts of Assets (Liabilities)	30	43
Noncurrent
Fair value of derivative assets
Gross Amounts of Recognized Assets (Liabilities)	51	77
Gross Amounts Offset	(30)	(29)
Net Amounts of Assets (Liabilities)	21	48
Noncurrent | CECONY | Subsidiaries
Fair value of derivative assets
Gross Amounts of Recognized Assets (Liabilities)	47	76
Gross Amounts Offset	(28)	(27)
Net Amounts of Assets (Liabilities)	19	49
Total fair value of derivative assets
Fair value of derivative assets
Gross Amounts of Recognized Assets (Liabilities)	135	160
Gross Amounts Offset	(79)	(67)
Net Amounts of Assets (Liabilities)	56	93
Net fair value derivative assets (liabilities)
Margin deposits assets	3	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)	125	154
Gross Amounts Offset	(76)	(62)
Net Amounts of Assets (Liabilities)	49	$ 92
Net fair value derivative assets (liabilities)
Margin deposits assets	$ 3