Other Postretirement Benefits - Periodic Postretirement Benefit Costs (Details) - Other Postretirement Benefits - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Service cost - including administrative expenses	$ 5	$ 7
Interest cost on projected other postretirement benefit obligation	9	8
Expected return on plan assets	(18)	(17)
Recognition of net actuarial loss	(1)	6
Recognition of prior service credit	0	(1)
TOTAL PERIODIC OTHER POSTRETIREMENT BENEFIT COST	(5)	3
Cost capitalized	(2)	(3)
Reconciliation to rate level	4	0
Total credit recognized	(3)	0
CECONY | Subsidiaries
Defined Benefit Plan Disclosure [Line Items]
Service cost - including administrative expenses	4	5
Interest cost on projected other postretirement benefit obligation	8	7
Expected return on plan assets	(14)	(14)
Recognition of net actuarial loss	(1)	5
Recognition of prior service credit	0	0
TOTAL PERIODIC OTHER POSTRETIREMENT BENEFIT COST	(3)	3
Cost capitalized	(2)	(2)
Reconciliation to rate level	4	(2)
Total credit recognized	$ (1)	$ (1)