Other Postretirement Benefits - Net Periodic Postretirement Benefit Costs (Details) - Other Postretirement Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 20	$ 20	$ 18
Interest cost on accumulated other postretirement benefit obligation	42	46	48
Expected return on plan assets	(73)	(69)	(77)
Recognition of net actuarial loss/(gain)	8	2	5
Recognition of prior service cost/(credit)	(6)	(17)	(20)
TOTAL PERIODIC POSTRETIREMENT BENEFIT COST/(CREDIT)	(9)	(18)	(26)
Cost capitalized	(8)	8	11
Reconciliation to rate level	8	(4)	22
Total expense/(credit) recognized	(9)	(14)	7
CECONY
Defined Benefit Plan Disclosure [Line Items]
Service cost	14	13	13
Interest cost on accumulated other postretirement benefit obligation	34	38	40
Expected return on plan assets	(63)	(61)	(67)
Recognition of net actuarial loss/(gain)	3	(3)	3
Recognition of prior service cost/(credit)	(2)	(11)	(14)
TOTAL PERIODIC POSTRETIREMENT BENEFIT COST/(CREDIT)	(14)	(24)	(25)
Cost capitalized	(6)	10	10
Reconciliation to rate level	9	(2)	22
Total expense/(credit) recognized	$ (11)	$ (16)	$ 7