Pension Benefits - Total Periodic Benefit Costs (Details) - Pension Benefits - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	$ 86	$ 73
Interest cost on projected benefit obligation	118	137
Expected return on plan assets	(276)	(258)
Recognition of net actuarial loss	199	175
Recognition of prior service credit	(4)	(4)
TOTAL PERIODIC BENEFIT COST	123	123
Cost capitalized	(39)	(31)
Reconciliation to rate level	(57)	(64)
Total expense/(credit) recognized	27	28
CECONY
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	81	69
Interest cost on projected benefit obligation	111	129
Expected return on plan assets	(262)	(245)
Recognition of net actuarial loss	189	165
Recognition of prior service credit	(5)	(5)
TOTAL PERIODIC BENEFIT COST	114	113
Cost capitalized	(37)	(29)
Reconciliation to rate level	(55)	(62)
Total expense/(credit) recognized	$ 22	$ 22