Other Postretirement Benefits - Periodic Postretirement Benefit Costs (Details) - Other Postretirement Benefits - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Defined Benefit Plan Disclosure [Line Items]
Service cost - including administrative expenses	$ 3	$ 3
Interest cost on projected other postretirement benefit obligation	12	12
Expected return on plan assets	(17)	(17)
Recognition of net actuarial gain	(7)	(5)
TOTAL PERIODIC OTHER POSTRETIREMENT CREDIT	(9)	(7)
Cost capitalized	(2)	(2)
Reconciliation to rate level	3	4
Total credit recognized	(8)	(5)
CECONY | Subsidiaries
Defined Benefit Plan Disclosure [Line Items]
Service cost - including administrative expenses	2	3
Interest cost on projected other postretirement benefit obligation	10	10
Expected return on plan assets	(13)	(14)
Recognition of net actuarial gain	(4)	(3)
TOTAL PERIODIC OTHER POSTRETIREMENT CREDIT	(5)	(4)
Cost capitalized	(1)	(1)
Reconciliation to rate level	2	2
Total credit recognized	$ (4)	$ (3)