Derivative Instruments and Hedging Activities - Schedule of Realized and Unrealized Gains (Losses) on Commodity Derivatives (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	$ 13	$ 100
Net deferred gains (losses)	260	84
Other operations and maintenance	3
Regulatory Liabilities, Current
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	64	87
Deferred Gain Loss Liability	247	(16)
Regulatory Liabilities, Noncurrent
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(51)	13
Regulatory Assets Current
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Deferred Gain Loss Liability	21	(105)
Recoverable Energy Costs, Current
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Deferred Gain Loss Liability	231	131
Regulatory Assets Non Current
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Deferred Gain Loss Liability	(5)	(42)
CECONY | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	10	91
Net deferred gains (losses)	236	76
Other operations and maintenance	3
CECONY | Regulatory Liabilities, Current | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	58	79
Deferred Gain Loss Liability	226	(15)
CECONY | Regulatory Liabilities, Noncurrent | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains (losses)	(48)	12
CECONY | Regulatory Assets Current | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Deferred Gain Loss Liability	20	(98)
CECONY | Recoverable Energy Costs, Current | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Deferred Gain Loss Liability	212	122
CECONY | Regulatory Assets Non Current | Subsidiaries
Pre-tax gains (losses) deferred in accordance with accounting rules for regulated operations:
Deferred Gain Loss Liability	$ (6)	$ (39)