Pension Benefits - Total Periodic Benefit Costs (Details) - Pension Benefits - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	$ 85	$ 73	$ 257	$ 220
Interest cost on projected benefit obligation	118	137	353	412
Expected return on plan assets	(274)	(258)	(822)	(775)
Recognition of net actuarial loss	197	175	590	524
Recognition of prior service credit	(4)	(4)	(12)	(12)
TOTAL PERIODIC BENEFIT COST	122	123	366	369
Cost capitalized	(41)	(34)	(120)	(98)
Reconciliation to rate level	(54)	(62)	(165)	(188)
Total credit recognized	27	27	81	83
CECONY | Subsidiaries
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	80	69	241	206
Interest cost on projected benefit obligation	111	129	332	387
Expected return on plan assets	(260)	(245)	(779)	(735)
Recognition of net actuarial loss	187	165	559	496
Recognition of prior service credit	(5)	(5)	(15)	(15)
TOTAL PERIODIC BENEFIT COST	113	113	338	339
Cost capitalized	(39)	(32)	(113)	(93)
Reconciliation to rate level	(52)	(59)	(158)	(179)
Total credit recognized	$ 22	$ 22	$ 67	$ 67