Fair Value Measurements - Reconciliation of Assets and Liabilities Measured at Level 3 Fair Value (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (15)	$ (8)
Included in earnings	(2)	(2)
Included in regulatory assets and liabilities	0	1
Settlements	4	5
Transfer out of level 3	0	4
Ending balance	(13)	0
CECONY | Subsidiaries
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(6)	(5)
Included in earnings	0	(1)
Included in regulatory assets and liabilities	0	0
Settlements	1	2
Transfer out of level 3	0	4
Ending balance	$ (5)	$ 0