Pension Benefits - Total Periodic Benefit Costs (Details) - Pension Benefits - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	$ 85	$ 73	$ 171	$ 147
Interest cost on projected benefit obligation	118	137	236	275
Expected return on plan assets	(274)	(258)	(548)	(517)
Recognition of net actuarial loss	197	175	393	349
Recognition of prior service credit	(4)	(4)	(8)	(8)
TOTAL PERIODIC BENEFIT COST	122	123	244	246
Cost capitalized	(41)	(33)	(79)	(64)
Reconciliation to rate level	(54)	(62)	(111)	(126)
Total credit recognized	27	28	54	56
CECONY | Subsidiaries
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	80	69	160	137
Interest cost on projected benefit obligation	111	129	222	258
Expected return on plan assets	(260)	(245)	(520)	(490)
Recognition of net actuarial loss	187	165	373	331
Recognition of prior service credit	(5)	(5)	(10)	(10)
TOTAL PERIODIC BENEFIT COST	113	113	225	226
Cost capitalized	(39)	(32)	(75)	(61)
Reconciliation to rate level	(52)	(59)	(106)	(121)
Total credit recognized	$ 22	$ 22	$ 44	$ 44