Regulatory Matters - Regulatory Assets (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	$ 4,237	$ 4,294
Regulatory assets – current	97	76
Total Regulatory Assets	4,334	4,370
Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,042	2,238
Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	787	810
Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	304	291
MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	241	229
Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	127	101
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	117	17
Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	76	67
Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	73	73
Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	72	76
System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	48	72
Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	35	36
Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	34	39
Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	32	36
Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	23	23
Recoverable REV demonstration project costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	20	20
Gate station upgrade project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	17	17
Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	4	5
O&R transition bond charges
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	1	2
Indian Point Energy Center program costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	13
Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	184	129
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	75	36
Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – current	22	40
CECONY
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	3,894	3,923
Regulatory assets – current	82	64
Total Regulatory Assets	3,976	3,987
CECONY | Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	1,934	2,111
CECONY | Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	696	716
CECONY | Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	291	278
CECONY | MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	241	229
CECONY | Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	115	86
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	106	11
CECONY | Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	76	67
CECONY | Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	54	56
CECONY | Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	0
CECONY | System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	47	70
CECONY | Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	35	36
CECONY | Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	34	39
CECONY | Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	30	34
CECONY | Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	23	23
CECONY | Recoverable REV demonstration project costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	18	18
CECONY | Gate station upgrade project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	17	17
CECONY | Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	4	5
CECONY | O&R transition bond charges
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	0
CECONY | Indian Point Energy Center program costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	13
CECONY | Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	173	114
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	63	29
CECONY | Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – current	$ 19	$ 35