Derivative Instruments and Hedging Activities - Realized and Unrealized Gains (Losses) on Commodity Derivatives (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	$ 100	$ 41
Total deferred gains (losses)	(16)	(17)
Net deferred gains (losses)	$ 84	$ 24
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Operating costs	Operating costs
Pre-tax gains (losses) recognized in income
Total pre-tax gains (losses) recognized in income	$ 0	$ 1
Regulatory Liabilities, Current
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	87	43
Regulatory Liabilities, Noncurrent
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	13	(2)
Regulatory Assets Current
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(105)	67
Recoverable Energy Costs, Current
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	131	(114)
Regulatory Assets Non Current
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(42)	30
CECONY | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	91	38
Total deferred gains (losses)	(15)	(15)
Net deferred gains (losses)	76	23
Pre-tax gains (losses) recognized in income
Total pre-tax gains (losses) recognized in income	0	1
CECONY | Regulatory Liabilities, Current | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	79	40
CECONY | Regulatory Liabilities, Noncurrent | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	12	(2)
CECONY | Regulatory Assets Current | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(98)	63
CECONY | Recoverable Energy Costs, Current | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	122	(104)
CECONY | Regulatory Assets Non Current | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	$ (39)	$ 26