Fair Value Measurements - Schedule of Reconciliation of Assets and Liabilities Measured at Level 3 Fair Value (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (5)	$ (15)
Included in earnings	(2)	(2)
Included in regulatory assets and liabilities	12	0
Settlements	4	4
Transfer out of level 3	(1)	0
Ending balance	8	(13)
CECONY | Subsidiaries
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(3)	(6)
Included in earnings	(1)	0
Included in regulatory assets and liabilities	6	0
Settlements	2	1
Transfer out of level 3	(1)	0
Ending balance	$ 3	$ (5)