Derivative Instruments and Hedging Activities - Realized and Unrealized Gains (Losses) on Commodity Derivatives (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	$ (78)	$ (52)	$ (37)	$ (327)
Total deferred gains (losses)	(1)	55	(18)	(385)
Net deferred gains (losses)	(79)	3	(55)	(712)
Pre-tax gains (losses) recognized in income
Total pre-tax gains (losses) recognized in income			1	26
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			1	0
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)	(57)	(61)	(14)	(210)
Regulatory Liabilities, Noncurrent
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(21)	9	(23)	(117)
Regulatory Assets Current
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	55	40	122	25
Recoverable Energy Costs, Current
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(74)	(84)	(188)	(376)
Regulatory Assets Non Current
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	18	99	48	(34)
CECONY | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(78)	(49)	(40)	(298)
Total deferred gains (losses)	3	52	(12)	(364)
Net deferred gains (losses)	(75)	3	(52)	(662)
Pre-tax gains (losses) recognized in income
Total pre-tax gains (losses) recognized in income			1	0
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			1	0
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)	(55)	(57)	(15)	(194)
CECONY | Regulatory Liabilities, Noncurrent | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(23)	8	(25)	(104)
CECONY | Regulatory Assets Current | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	54	37	117	25
CECONY | Recoverable Energy Costs, Current | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(68)	(81)	(172)	(355)
CECONY | Regulatory Assets Non Current | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	$ 17	$ 96	$ 43	$ (34)