Regulatory Matters - Regulatory Assets (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	$ 4,097	$ 4,266
Regulatory assets – current	90	67
Total Regulatory Assets	4,187	4,333
Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,167	2,526
Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	772	793
Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	276	260
MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	150	50
Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	74	79
Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	77	51
Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	72	56
Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	66	60
Regulatory assets – current	46	27
Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	82	38
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	36	44
Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	34	37
Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	33	18
Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	30	37
Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	24	24
Indian Point Energy Center program costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	20	29
Recoverable REV demonstration project expenses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	18	19
Gate station upgrade project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	14	13
Net electric deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	8	9
Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	6	10
O&R transition bond charges
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	5	9
Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	133	104
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	44	40
CECONY
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	3,694	3,863
Regulatory assets – current	85	62
Total Regulatory Assets	3,779	3,925
CECONY | Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,039	2,376
CECONY | Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	662	677
CECONY | Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	264	248
CECONY | MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	150	50
CECONY | Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	57	58
CECONY | Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	57	25
CECONY | Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	72	56
CECONY | Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	59	52
Regulatory assets – current	46	25
CECONY | Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	0
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	30	37
CECONY | Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	32	35
CECONY | Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	33	18
CECONY | Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	30	37
CECONY | Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	24	24
CECONY | Indian Point Energy Center program costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	20	29
CECONY | Recoverable REV demonstration project expenses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	16	17
CECONY | Gate station upgrade project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	14	13
CECONY | Net electric deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	8	9
CECONY | Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	6	10
CECONY | O&R transition bond charges
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	0
CECONY | Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	121	92
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	$ 39	$ 37