Other Postretirement Benefits - Periodic Postretirement Benefit Costs (Details) - Other Postretirement Benefits - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Service cost - including administrative expenses	$ 4	$ 5
Interest cost on projected other postretirement benefit obligation	14	9
Expected return on plan assets	(18)	(18)
Recognition of net actuarial gain	(4)	(1)
TOTAL PERIODIC OTHER POSTRETIREMENT BENEFIT CREDIT	(4)	(5)
Cost capitalized	(2)	(2)
Reconciliation to rate level	1	4
Total expense (credit) recognized	(5)	(3)
CECONY | Subsidiaries
Defined Benefit Plan Disclosure [Line Items]
Service cost - including administrative expenses	3	4
Interest cost on projected other postretirement benefit obligation	12	8
Expected return on plan assets	(14)	(14)
Recognition of net actuarial gain	(2)	(1)
TOTAL PERIODIC OTHER POSTRETIREMENT BENEFIT CREDIT	(1)	(3)
Cost capitalized	(1)	(2)
Reconciliation to rate level	0	4
Total expense (credit) recognized	$ (2)	$ (1)