Other Postretirement Benefits - Periodic Postretirement Benefit Costs (Details) - Other Postretirement Benefits - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Service cost - including administrative expenses	$ 4	$ 5	$ 11	$ 14
Interest cost on projected other postretirement benefit obligation	14	8	43	26
Expected return on plan assets	(18)	(18)	(53)	(54)
Recognition of net actuarial gain	(4)	(4)	(12)	(11)
Recognition of prior service credit	0	0	(1)	(1)
TOTAL PERIODIC OTHER POSTRETIREMENT CREDIT	(4)	(9)	(12)	(26)
Cost capitalized	(2)	(2)	(5)	(6)
Reconciliation to rate level	1	7	2	22
Total credit recognized	(5)	(4)	(15)	(10)
CECONY | Subsidiaries
Defined Benefit Plan Disclosure [Line Items]
Service cost - including administrative expenses	3	4	9	11
Interest cost on projected other postretirement benefit obligation	12	8	37	23
Expected return on plan assets	(14)	(14)	(42)	(43)
Recognition of net actuarial gain	(2)	(3)	(6)	(7)
Recognition of prior service credit	0	0	0	0
TOTAL PERIODIC OTHER POSTRETIREMENT CREDIT	(1)	(5)	(2)	(16)
Cost capitalized	(2)	(2)	(4)	(5)
Reconciliation to rate level	0	6	(2)	18
Total credit recognized	$ (3)	$ (1)	$ (8)	$ (3)