Regulatory Matters - Regulatory Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	$ 4,859	$ 4,294
Regulatory assets – current	128	76
Total Regulatory Assets	4,987	4,370
Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,541	2,238
Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	732	810
Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	321	291
MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	248	229
Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	219	101
Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	77	76
Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	71	73
Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	75	67
System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	131	72
Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	39	39
Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	28	36
Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	35	36
Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	22	23
Recoverable REV demonstration project costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	21	20
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	83	17
Gate station upgrade project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	19	17
Non-wire alternative projects
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	14	3
Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	3	5
Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – current	0	40
O&R transition bond charges
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	2
Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	180	139
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	128	36
CECONY
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	4,487	3,923
Regulatory assets – current	113	64
Total Regulatory Assets	4,600	3,987
CECONY | Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,403	2,111
CECONY | Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	647	716
CECONY | Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	308	278
CECONY | MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	248	229
CECONY | Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	210	86
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	47	56
CECONY | Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	75	67
CECONY | System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	130	70
CECONY | Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	39	39
CECONY | Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	26	34
CECONY | Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	35	36
CECONY | Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	22	23
CECONY | Recoverable REV demonstration project costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	19	18
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	76	11
CECONY | Gate station upgrade project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	19	17
CECONY | Non-wire alternative projects
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	14	3
CECONY | Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	3	5
CECONY | Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – current	0	35
CECONY | O&R transition bond charges
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	0
CECONY | Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	166	124
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	$ 113	$ 29