Regulatory Matters - Regulatory Assets (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	$ 4,732	$ 4,859
Regulatory assets – current	143	128
Total Regulatory Assets	4,875	4,987
Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,246	2,541
Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	735	732
Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	333	321
Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	229	219
MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	224	248
Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	197	71
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	128	83
System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	115	131
Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	78	75
Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	73	77
Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	39	39
Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	34	35
Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	26	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
Gate station upgrade project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	19	19
Non-wire alternative projects
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	14	14
Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2	3
Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	195	180
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	142	128
Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – current	1	0
CECONY
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	4,365	4,487
Regulatory assets – current	125	113
Total Regulatory Assets	4,490	4,600
CECONY | Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,113	2,403
CECONY | Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	652	647
CECONY | Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	318	308
CECONY | Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	222	210
CECONY | MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	224	248
CECONY | Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	169	47
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	118	76
CECONY | System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	114	130
CECONY | Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	78	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	39	39
CECONY | Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	34	35
CECONY | Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	24	26
CECONY | Recoverable REV demonstration project costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	20	19
CECONY | Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	22	22
CECONY | Gate station upgrade project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	19	19
CECONY | Non-wire alternative projects
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	14	14
CECONY | Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2	3
CECONY | Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	183	166
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	125	113
CECONY | Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – current	$ 0	$ 0