Regulatory Matters - Regulatory Assets (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	$ 4,245	$ 4,294
Regulatory assets – current	43	76
Total Regulatory Assets	4,288	4,370
Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,166	2,238
Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	798	810
Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	299	291
MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	239	229
Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	114	101
Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	77	76
Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	75	67
Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	63	73
System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	60	72
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	43	17
Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	37	39
Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	36	36
Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	34	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	18	17
Indian Point Energy Center program costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	7	13
Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	6	5
O&R transition bond charges
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	1	2
Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	129	129
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	39	36
Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – current	4	40
CECONY
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	3,895	3,923
Regulatory assets – current	29	64
Total Regulatory Assets	3,924	3,987
CECONY | Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,052	2,111
CECONY | Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	706	716
CECONY | Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	286	278
CECONY | MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	239	229
CECONY | Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	101	86
CECONY | Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	0
CECONY | Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	75	67
CECONY | Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	45	56
CECONY | System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	59	70
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	37	11
CECONY | Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	37	39
CECONY | Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	36	36
CECONY | Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	32	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	18	17
CECONY | Indian Point Energy Center program costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	7	13
CECONY | Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	6	5
CECONY | O&R transition bond charges
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	0
CECONY | Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	118	114
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	29	29
CECONY | Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – current	$ 0	$ 35