Other Postretirement Benefits - Net Periodic Postretirement Benefit Costs (Details) - Other Postretirement Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 18	$ 20	$ 20
Interest cost on accumulated other postretirement benefit obligation	44	42	46
Expected return on plan assets	(66)	(73)	(69)
Recognition of net actuarial loss/(gain)	(9)	8	2
Recognition of prior service credit	(2)	(6)	(17)
TOTAL PERIODIC POSTRETIREMENT BENEFIT CREDIT	(15)	(9)	(18)
Cost capitalized	(7)	(8)	8
Reconciliation to rate level	12	8	(4)
Total credit recognized	(10)	(9)	(14)
CECONY
Defined Benefit Plan Disclosure [Line Items]
Service cost	13	14	13
Interest cost on accumulated other postretirement benefit obligation	36	34	38
Expected return on plan assets	(54)	(63)	(61)
Recognition of net actuarial loss/(gain)	(10)	3	(3)
Recognition of prior service credit	(2)	(2)	(11)
TOTAL PERIODIC POSTRETIREMENT BENEFIT CREDIT	(17)	(14)	(24)
Cost capitalized	(5)	(6)	10
Reconciliation to rate level	7	9	(2)
Total credit recognized	$ (15)	$ (11)	$ (16)