Other Postretirement Benefits - Schedule of Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	$ 330
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	326	$ 330
CECONY
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	301
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	301	301
Other Postretirement Benefits
CHANGE IN BENEFIT OBLIGATION
Projected benefit obligation at beginning of year	1,219	1,198	$ 1,287
Service cost	20	20	18
Interest cost on accumulated other postretirement benefit obligation	42	46	48
Net actuarial loss/(gain)	(70)	53	(57)
Benefits paid and administrative expenses, net of subsidies	(135)	(134)	(134)
Participant contributions	38	36	36
PROJECTED BENEFIT OBLIGATION AT END OF YEAR	1,114	1,219	1,198
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	1,039	975	994
Actual return on plan assets	(66)	150	60
Employer contributions	6	17	7
Employer group waiver plan subsidies	34	34	35
Participant contributions	37	35	36
Benefits paid	(165)	(172)	(157)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	885	1,039	975
FUNDED STATUS	(229)	(180)	(223)
Unrecognized net loss/(gain)	14	(47)	(24)
Unrecognized prior service costs	(8)	(14)	(31)
Other Postretirement Benefits | CECONY
CHANGE IN BENEFIT OBLIGATION
Projected benefit obligation at beginning of year	985	1,007	1,093
Service cost	14	13	13
Interest cost on accumulated other postretirement benefit obligation	34	38	40
Net actuarial loss/(gain)	(32)	16	(52)
Benefits paid and administrative expenses, net of subsidies	(125)	(124)	(122)
Participant contributions	37	35	35
PROJECTED BENEFIT OBLIGATION AT END OF YEAR	913	985	1,007
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	893	851	870
Actual return on plan assets	(54)	130	52
Employer contributions	6	8	7
Employer group waiver plan subsidies	32	30	33
Participant contributions	37	35	35
Benefits paid	(155)	(161)	(146)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	759	893	851
FUNDED STATUS	(154)	(92)	(156)
Unrecognized net loss/(gain)	(2)	(85)	(42)
Unrecognized prior service costs	$ (5)	$ (7)	$ (18)