Other Postretirement Benefits - Periodic Postretirement Benefit Costs (Details) - Other Postretirement Benefits - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Defined Benefit Plan Disclosure [Line Items]
Service cost - including administrative expenses	$ 3	$ 3	$ 8	$ 9
Interest cost on projected other postretirement benefit obligation	12	12	36	35
Expected return on plan assets	(17)	(17)	(50)	(51)
Recognition of net actuarial gain	(7)	(5)	(20)	(14)
Recognition of prior service credit			(1)	(1)
TOTAL PERIODIC OTHER POSTRETIREMENT CREDIT	(9)	(7)	(27)	(22)
Cost capitalized	(1)	(2)	(4)	(4)
Reconciliation to rate level	3	4	9	12
Total credit recognized	(7)	(5)	(22)	(14)
CECONY | Subsidiaries
Defined Benefit Plan Disclosure [Line Items]
Service cost - including administrative expenses	2	3	7	8
Interest cost on projected other postretirement benefit obligation	10	10	31	30
Expected return on plan assets	(13)	(14)	(40)	(41)
Recognition of net actuarial gain	(4)	(4)	(13)	(11)
Recognition of prior service credit			0	0
TOTAL PERIODIC OTHER POSTRETIREMENT CREDIT	(5)	(5)	(15)	(14)
Cost capitalized	(1)	(1)	(3)	(4)
Reconciliation to rate level	2	3	6	10
Total credit recognized	$ (4)	$ (3)	$ (12)	$ (8)