Regulatory Matters - Regulatory Assets (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	$ 4,606	$ 4,859
Regulatory assets – current	117	128
Total Regulatory Assets	4,723	4,987
Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,072	2,541
Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	729	732
Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	336	321
Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	235	219
Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	229	71
MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	212	248
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	142	83
System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	103	131
Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	72	75
Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	70	77
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	34	35
Gate station upgrade project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	28	19
Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	24	28
Recoverable REV demonstration project costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	23	21
Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	22	22
Non-wire alternative projects
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	14	14
Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	3
Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	224	180
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	106	128
Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – current	11	0
CECONY
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	4,252	4,487
Regulatory assets – current	97	113
Total Regulatory Assets	4,349	4,600
CECONY | Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	1,947	2,403
CECONY | Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	648	647
CECONY | Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	322	308
CECONY | Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	230	210
CECONY | Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	196	47
CECONY | MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	212	248
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	133	76
CECONY | System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	102	130
CECONY | Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	72	75
CECONY | Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	0
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	34	35
CECONY | Gate station upgrade project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	28	19
CECONY | Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	22	26
CECONY | Recoverable REV demonstration project costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	21	19
CECONY | Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	22	22
CECONY | Non-wire alternative projects
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	14	14
CECONY | Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	3
CECONY | Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	212	166
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	93	113
CECONY | Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – current	$ 4	$ 0