Pension Benefits - Schedule of Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	$ 326
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	397	$ 326
Pension Benefits
CHANGE IN PROJECTED BENEFIT OBLIGATION
Projected benefit obligation at beginning of year	14,449	15,536	$ 14,095
Service cost – excluding administrative expenses	245	286	259
Interest cost on projected benefit obligation	601	561	591
Net actuarial loss/(gain)	2,191	(1,219)	1,231
Plan amendments	15	0	6
Benefits paid	(709)	(715)	(646)
PROJECTED BENEFIT OBLIGATION AT END OF YEAR	16,792	14,449	15,536
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	13,450	14,274	12,472
Actual return on plan assets	2,556	(536)	2,041
Employer contributions	350	473	450
Benefits paid	(709)	(715)	(646)
Administrative expenses	(39)	(46)	(43)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	15,608	13,450	14,274
FUNDED STATUS	(1,184)	(999)	(1,262)
Unrecognized net loss	2,604	2,464	2,760
Unrecognized prior service costs	(173)	(205)	(223)
Accumulated benefit obligation	15,015	13,030	13,897
CECONY
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	301
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	371	301
CECONY | Pension Benefits
CHANGE IN PROJECTED BENEFIT OBLIGATION
Projected benefit obligation at beginning of year	13,542	14,567	13,203
Service cost – excluding administrative expenses	228	267	241
Interest cost on projected benefit obligation	564	525	554
Net actuarial loss/(gain)	2,076	(1,159)	1,171
Plan amendments	0	0	0
Benefits paid	(660)	(658)	(602)
PROJECTED BENEFIT OBLIGATION AT END OF YEAR	15,750	13,542	14,567
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	12,744	13,519	11,815
Actual return on plan assets	2,425	(507)	1,935
Employer contributions	318	434	412
Benefits paid	(660)	(658)	(602)
Administrative expenses	(37)	(44)	(41)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	14,790	12,744	13,519
FUNDED STATUS	(960)	(798)	(1,048)
Unrecognized net loss	2,466	2,338	2,624
Unrecognized prior service costs	(202)	(222)	(242)
Accumulated benefit obligation	$ 14,010	$ 12,161	$ 12,972