Regulatory Matters - Regulatory Assets (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	$ 5,990	$ 6,195
Regulatory assets – current	253	266
Total Regulatory Assets	6,243	6,461
Regulatory assets not earning return	4,458	4,766
Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,943	3,241
Regulatory assets not earning return	2,943	3,241
Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	858	865
Regulatory assets not earning return	847	855
Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	369	356
Regulatory assets not earning return	350	336
Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	244	241
Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	365	315
MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	176	188
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	97	120
Regulatory assets not earning return	97	120
System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	106	124
Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	56	62
COVID-19 pandemic deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	142	115
Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	238	195
Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	36	36
Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	32	32
Gate station upgrade project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	18	25
Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	19	21
Recoverable REV demonstration project costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	18	20
Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	21	21
Non-wire alternative projects
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	19	18
Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	233	200
Regulatory assets not earning return	35	24
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	186	190
Regulatory assets not earning return	186	190
Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – current	67	76
CECONY
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	5,559	5,745
Regulatory assets – current	234	244
Total Regulatory Assets	5,793	5,989
Regulatory assets not earning return	4,203	4,481
CECONY | Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,791	3,065
Regulatory assets not earning return	2,791	3,065
CECONY | Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	786	791
Regulatory assets not earning return	776	781
CECONY | Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	353	342
Regulatory assets not earning return	336	323
CECONY | Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	243	239
CECONY | Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	318	272
CECONY | MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	176	188
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	91	111
Regulatory assets not earning return	91	111
CECONY | System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	105	124
CECONY | Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	56	62
CECONY | COVID-19 pandemic deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	139	113
CECONY | Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	119	83
CECONY | Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	36	36
CECONY | Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	32	32
CECONY | Gate station upgrade project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	18	25
CECONY | Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	18	19
CECONY | Recoverable REV demonstration project costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	17	18
CECONY | Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	21	21
CECONY | Non-wire alternative projects
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	19	18
CECONY | Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	221	186
Regulatory assets not earning return	35	24
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	174	177
Regulatory assets not earning return	174	177
CECONY | Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – current	$ 60	$ 67