Regulatory Matters - Regulatory Assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	$ 4,294	$ 4,266
Regulatory assets – current	76	67
Total Regulatory Assets	4,370	4,333
Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,238	2,526
Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	810	793
Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	291	260
MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	229	50
Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	101	51
Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	76	38
Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	73	79
Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	67	56
System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	72	14
Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	39	37
Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	36	37
Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	36	18
Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	23	24
Recoverable REV demonstration project costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	20	19
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	17	44
Gate Station Upgrade Project [Member]
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	17	13
Indian Point Energy Center program costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	13	29
Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	5	10
Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	3	60
Regulatory assets – current	40	27
O&R transition bond charges
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2	9
Surcharge for New York State assessment
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	2
Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	126	97
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	36	40
CECONY
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	3,923	3,863
Regulatory assets – current	64	62
Total Regulatory Assets	3,987	3,925
CECONY | Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,111	2,376
CECONY | Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	716	677
CECONY | Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	278	248
CECONY | MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	229	50
CECONY | Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	86	25
CECONY | Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	0
CECONY | Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	56	58
CECONY | Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	67	56
CECONY | System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	70	14
CECONY | Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	39	37
CECONY | Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	34	35
CECONY | Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	36	18
CECONY | Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	23	24
CECONY | Recoverable REV demonstration project costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	18	17
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	11	37
CECONY | Gate Station Upgrade Project [Member]
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	17	13
CECONY | Indian Point Energy Center program costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	13	29
CECONY | Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	5	10
CECONY | Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	52
Regulatory assets – current	35	25
CECONY | O&R transition bond charges
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	0
CECONY | Surcharge for New York State assessment
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	2
CECONY | Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	114	85
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	$ 29	$ 37