Pension Benefits - Schedule of Funded Status (Details) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CHANGE IN PROJECTED BENEFIT OBLIGATION
Projected benefit obligation at beginning of year	$ 14,377	$ 15,081	$ 12,197
Service cost – excluding administrative expenses	271	293	221
Interest cost on projected benefit obligation	596	575	572
Net actuarial (gain)/loss	(302)	(996)	2,641
Plan amendments	(256)	0	6
Benefits paid	(591)	(576)	(556)
PROJECTED BENEFIT OBLIGATION AT END OF YEAR	14,095	14,377	15,081
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	11,759	11,495	10,755
Actual return on plan assets	829	126	752
Employer contributions	508	750	578
Benefits paid	(591)	(576)	(556)
Administrative expenses	(33)	(36)	(34)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	12,472	11,759	11,495
FUNDED STATUS	(1,623)	(2,618)	(3,586)
Unrecognized net loss	3,157	3,909	4,888
Unrecognized prior service costs	(244)	16	20
Accumulated benefit obligation	12,655	12,909	13,454
CECONY
CHANGE IN PROJECTED BENEFIT OBLIGATION
Projected benefit obligation at beginning of year	13,482	14,137	11,429
Service cost – excluding administrative expenses	254	274	206
Interest cost on projected benefit obligation	559	538	536
Net actuarial (gain)/loss	(282)	(931)	2,484
Plan amendments	(259)	0	0
Benefits paid	(551)	(536)	(518)
PROJECTED BENEFIT OBLIGATION AT END OF YEAR	13,203	13,482	14,137
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	11,141	10,897	10,197
Actual return on plan assets	787	118	715
Employer contributions	469	697	535
Benefits paid	(551)	(536)	(518)
Administrative expenses	(31)	(35)	(32)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	11,815	11,141	10,897
FUNDED STATUS	(1,388)	(2,341)	(3,240)
Unrecognized net loss	2,995	3,704	4,616
Unrecognized prior service costs	(258)	3	4
Accumulated benefit obligation	$ 11,806	$ 12,055	$ 12,553