Derivative Instruments and Hedging Activities - Realized and Unrealized Gains (Losses) on Commodity Derivatives (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	$ (38)	$ (22)	$ (75)	$ (349)
Total deferred gains (losses)	(138)	(110)	(156)	(495)
Net deferred gains (losses)	$ (176)	$ (132)	$ (231)	$ (844)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Operating costs	Operating costs	Operating costs	Operating costs
Pre-tax gains (losses) recognized in income
Total pre-tax gains (losses) recognized in income	$ (1)	$ 1	$ 0	$ 27
Gas purchased for resale
Pre-tax gains (losses) recognized in income
Total pre-tax gains (losses) recognized in income			0	4
Non-utility revenue
Pre-tax gains (losses) recognized in income
Total pre-tax gains (losses) recognized in income			0	17
Other operations and maintenance expense
Pre-tax gains (losses) recognized in income
Total pre-tax gains (losses) recognized in income			0	1
Other interest expense
Pre-tax gains (losses) recognized in income
Total pre-tax gains (losses) recognized in income			0	5
Regulatory Liabilities, Current
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(31)	(11)	(45)	(221)
Regulatory Liabilities, Noncurrent
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(7)	(11)	(30)	(128)
Regulatory Assets Current
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(18)	22	104	47
Recoverable Energy Costs, Current
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(81)	(98)	(269)	(474)
Regulatory Assets Non Current
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(39)	(34)	9	(68)
CECONY | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(32)	(18)	(72)	(316)
Total deferred gains (losses)	(124)	(103)	(136)	(467)
Net deferred gains (losses)	(156)	(121)	(208)	(783)
Pre-tax gains (losses) recognized in income
Total pre-tax gains (losses) recognized in income	(1)	1	0	1
CECONY | Gas purchased for resale | Subsidiaries
Pre-tax gains (losses) recognized in income
Total pre-tax gains (losses) recognized in income			0	0
CECONY | Non-utility revenue | Subsidiaries
Pre-tax gains (losses) recognized in income
Total pre-tax gains (losses) recognized in income			0	0
CECONY | Other operations and maintenance expense | Subsidiaries
Pre-tax gains (losses) recognized in income
Total pre-tax gains (losses) recognized in income			0	1
CECONY | Other interest expense | Subsidiaries
Pre-tax gains (losses) recognized in income
Total pre-tax gains (losses) recognized in income			0	0
CECONY | Regulatory Liabilities, Current | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(27)	(9)	(42)	(203)
CECONY | Regulatory Liabilities, Noncurrent | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(5)	(9)	(30)	(113)
CECONY | Regulatory Assets Current | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(15)	20	102	45
CECONY | Recoverable Energy Costs, Current | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(75)	(94)	(247)	(449)
CECONY | Regulatory Assets Non Current | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	$ (34)	$ (29)	$ 9	$ (63)