Pension Benefits - Total Periodic Benefit Costs (Details) - Pension Benefits - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	$ 66	$ 69	$ 132	$ 138
Interest cost on projected benefit obligation	148	149	296	298
Expected return on plan assets	(243)	(237)	(484)	(474)
Recognition of net actuarial loss	149	149	297	298
Recognition of prior service costs	(4)	1	(9)	2
TOTAL PERIODIC BENEFIT COST	116	131	232	262
Cost capitalized	(51)	(53)	(94)	(106)
Reconciliation to rate level	(3)	13	(14)	26
Cost charged to operating expenses	62	91	124	182
CECONY
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	61	65	123	129
Interest cost on projected benefit obligation	139	140	277	280
Expected return on plan assets	(229)	(225)	(459)	(449)
Recognition of net actuarial loss	141	141	282	282
Recognition of prior service costs	(5)	0	(10)	1
TOTAL PERIODIC BENEFIT COST	107	121	213	243
Cost capitalized	(48)	(50)	(88)	(99)
Reconciliation to rate level	(5)	14	(16)	26
Cost charged to operating expenses	$ 54	$ 85	$ 109	$ 170