Other Postretirement Benefits - Schedule of Funded Status (Details) - Other Postretirement Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CHANGE IN BENEFIT OBLIGATION
Projected benefit obligation at beginning of year	$ 1,287	$ 1,411	$ 1,395
Service cost	18	20	19
Interest cost on accumulated other postretirement benefit obligation	48	51	60
Amendments	0	0	(12)
Net actuarial loss/(gain)	(57)	(103)	47
Benefits paid and administrative expenses	(134)	(127)	(134)
Participant contributions	36	35	36
PROJECTED BENEFIT OBLIGATION AT END OF YEAR	1,198	1,287	1,411
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	994	1,084	1,113
Actual return on plan assets	60	(6)	59
Employer contributions	7	6	7
EGWP payments	35	28	12
Participant contributions	36	35	36
Benefits paid	(157)	(153)	(143)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	975	994	1,084
FUNDED STATUS	(223)	(293)	(327)
Unrecognized net loss/(gain)	(24)	28	78
Unrecognized prior service costs	(31)	(51)	(71)
CECONY
CHANGE IN BENEFIT OBLIGATION
Projected benefit obligation at beginning of year	1,093	1,203	1,198
Service cost	13	15	15
Interest cost on accumulated other postretirement benefit obligation	40	43	52
Amendments	0	0	0
Net actuarial loss/(gain)	(52)	(85)	28
Benefits paid and administrative expenses	(122)	(117)	(125)
Participant contributions	35	34	35
PROJECTED BENEFIT OBLIGATION AT END OF YEAR	1,007	1,093	1,203
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	870	950	977
Actual return on plan assets	52	(4)	54
Employer contributions	7	6	7
EGWP payments	33	26	11
Participant contributions	35	34	35
Benefits paid	(146)	(142)	(134)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	851	870	950
FUNDED STATUS	(156)	(223)	(253)
Unrecognized net loss/(gain)	(42)	4	45
Unrecognized prior service costs	$ (18)	$ (32)	$ (46)