Pension Benefits - Total Periodic Benefit Costs (Details) - Pension Benefits - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	$ 66	$ 69
Interest cost on projected benefit obligation	148	149
Expected return on plan assets	(243)	(237)
Recognition of net actuarial loss	149	149
Recognition of prior service costs	(4)	1
TOTAL PERIODIC BENEFIT COST	116	131
Cost capitalized	(43)	(52)
Reconciliation to rate level	(11)	12
Cost charged to operating expenses	62	91
CECONY
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	61	65
Interest cost on projected benefit obligation	139	140
Expected return on plan assets	(229)	(225)
Recognition of net actuarial loss	141	141
Recognition of prior service costs	(5)	0
TOTAL PERIODIC BENEFIT COST	107	121
Cost capitalized	(41)	(49)
Reconciliation to rate level	(12)	13
Cost charged to operating expenses	$ 54	$ 85