Pension Benefits - Schedule of Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	$ 397
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	465	$ 397
Pension Benefits
CHANGE IN PROJECTED BENEFIT OBLIGATION
Projected benefit obligation at beginning of year	16,792	14,449	$ 15,536
Service cost – excluding administrative expenses	288	245	286
Interest cost on projected benefit obligation	549	601	561
Net actuarial loss/(gain)	2,281	2,191	(1,219)
Plan amendments	0	15	0
Benefits paid	(945)	(709)	(715)
PROJECTED BENEFIT OBLIGATION AT END OF YEAR	18,965	16,792	14,449
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	15,608	13,450	14,274
Actual return on plan assets	1,927	2,556	(536)
Employer contributions	475	350	473
Benefits paid	(945)	(709)	(715)
Administrative expenses	(43)	(39)	(46)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	17,022	15,608	13,450
FUNDED STATUS	(1,943)	(1,184)	(999)
Unrecognized net loss	3,330	2,604	2,464
Unrecognized prior service costs/(credits)	(156)	(173)	(205)
Accumulated benefit obligation	16,768	15,015	13,030
CECONY
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	371
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	439	371
CECONY | Pension Benefits
CHANGE IN PROJECTED BENEFIT OBLIGATION
Projected benefit obligation at beginning of year	15,750	13,542	14,567
Service cost – excluding administrative expenses	269	228	267
Interest cost on projected benefit obligation	515	564	525
Net actuarial loss/(gain)	2,154	2,076	(1,159)
Plan amendments	0	0	0
Benefits paid	(867)	(660)	(658)
PROJECTED BENEFIT OBLIGATION AT END OF YEAR	17,821	15,750	13,542
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	14,790	12,744	13,519
Actual return on plan assets	1,830	2,425	(507)
Employer contributions	435	318	434
Benefits paid	(867)	(660)	(658)
Administrative expenses	(41)	(37)	(44)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	16,147	14,790	12,744
FUNDED STATUS	(1,674)	(960)	(798)
Unrecognized net loss	3,145	2,466	2,338
Unrecognized prior service costs/(credits)	(183)	(202)	(222)
Accumulated benefit obligation	$ 15,676	$ 14,010	$ 12,161