Fair Value Measurements - Reconciliation of Assets and Liabilities Measured at Level 3 Fair Value (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (11)	$ (7)	$ (8)	$ 15
Included in earnings	(1)	2	(6)	(2)
Included in regulatory assets and liabilities	(15)	(3)	(13)	16
Settlements	2	(2)	7	0
Decrease due to the sale of the Clean Energy Businesses			0	(29)
Transfer out of level 3			(5)	(10)
Ending balance	(25)	(10)	(25)	(10)
CECONY | Subsidiaries
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(6)	(4)	(5)	(6)
Included in earnings	0	1	(2)	(1)
Included in regulatory assets and liabilities	(12)	(3)	(8)	10
Settlements	1	(1)	3	0
Decrease due to the sale of the Clean Energy Businesses			0	0
Transfer out of level 3			(5)	(10)
Ending balance	$ (17)	$ (7)	$ (17)	$ (7)