Derivative Instruments and Hedging Activities - Realized and Unrealized Gains (Losses) on Commodity Derivatives (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	$ 41	$ (275)
Total deferred gains/(losses)	(17)	(440)
Net deferred gains/(losses)	24	(715)
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)	43	(149)
Regulatory Liabilities, Noncurrent
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	(2)	(126)
Regulatory Assets Current
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	67	(16)
Recoverable Energy Costs, Current
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	(114)	(291)
Regulatory Assets Non Current
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	30	(133)
CECONY | Subsidiaries
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	38	(248)
Total deferred gains/(losses)	(15)	(416)
Net deferred gains/(losses)	23	(664)
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)	40	(137)
CECONY | Regulatory Liabilities, Noncurrent | Subsidiaries
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	(2)	(111)
CECONY | Regulatory Assets Current | Subsidiaries
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	63	(12)
CECONY | Recoverable Energy Costs, Current | Subsidiaries
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	(104)	(274)
CECONY | Regulatory Assets Non Current | Subsidiaries
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	$ 26	$ (130)