Fair Value Measurements - Reconciliation of Assets and Liabilities Measured at Level 3 Fair Value (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (13)	$ 0	$ (15)	$ (8)
Included in earnings	(1)	(2)	(3)	(5)
Included in regulatory assets and liabilities	(4)	(12)	(1)	(3)
Settlements	1	3	2	5
Ending balance	(17)	(11)	(17)	(11)
CECONY | Subsidiaries
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(5)	0	(6)	(5)
Included in earnings	0	(1)	0	(2)
Included in regulatory assets and liabilities	(3)	(6)	(2)	(1)
Settlements	0	1	0	2
Ending balance	$ (8)	$ (6)	$ (8)	$ (6)