Pension Benefits - Total Periodic Benefit Costs (Details) - Pension Benefits - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	$ 72	$ 66	$ 218	$ 197
Interest cost on projected benefit obligation	140	148	420	444
Expected return on plan assets	(258)	(243)	(775)	(726)
Recognition of net actuarial loss	172	149	516	446
Recognition of prior service cost/(credit)	(4)	(4)	(13)	(13)
TOTAL PERIODIC BENEFIT COST	122	116	366	348
Cost capitalized	(32)	(40)	(94)	(134)
Reconciliation to rate level	(22)	(14)	(68)	(28)
Total expense/(credit) recognized	68	62	204	186
CECONY
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	68	61	204	184
Interest cost on projected benefit obligation	131	139	394	416
Expected return on plan assets	(245)	(229)	(734)	(689)
Recognition of net actuarial loss	163	141	488	423
Recognition of prior service cost/(credit)	(5)	(5)	(15)	(14)
TOTAL PERIODIC BENEFIT COST	112	107	337	320
Cost capitalized	(30)	(37)	(89)	(125)
Reconciliation to rate level	(24)	(16)	(74)	(32)
Total expense/(credit) recognized	$ 58	$ 54	$ 174	$ 163