Regulatory Matters - Regulatory Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	$ 4,652	$ 4,827
Regulatory liabilities – current	63	102
Total Regulatory Liabilities	4,715	4,929
Future income tax
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	2,323	2,426
Allowance for cost of removal less salvage
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	1,035	989
TCJA net benefits
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	379	471
Net proceeds from sale of property
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	159	173
Net unbilled revenue deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	155	199
Energy efficiency portfolio standard unencumbered funds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	88	122
Pension and other postretirement benefit deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	72	75
System benefit charge carrying charge
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	56	48
Property tax refunds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	38	45
Unrecognized other postretirement costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	33	9
BQDM and REV Demo reconciliations
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	26	27
Settlement of gas proceedings
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	22	10
Sales and use tax refunds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	18	8
Earnings sharing - electric, gas and steam
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	17	22
Settlement of prudence proceeding
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	7	8
Other
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	224	195
Refundable energy costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	31	44
Deferred derivative gains
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	32	34
Revenue decoupling mechanism
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	0	24
CECONY
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	4,222	4,427
Regulatory liabilities – current	39	63
Total Regulatory Liabilities	4,261	4,490
CECONY | Future income tax
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	2,175	2,275
CECONY | Allowance for cost of removal less salvage
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	884	843
CECONY | TCJA net benefits
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	366	454
CECONY | Net proceeds from sale of property
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	159	173
CECONY | Net unbilled revenue deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	155	199
CECONY | Energy efficiency portfolio standard unencumbered funds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	85	118
CECONY | Pension and other postretirement benefit deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	40	46
CECONY | System benefit charge carrying charge
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	50	44
CECONY | Property tax refunds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	38	45
CECONY | Unrecognized other postretirement costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	0	0
CECONY | BQDM and REV Demo reconciliations
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	25	26
CECONY | Settlement of gas proceedings
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	22	10
CECONY | Sales and use tax refunds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	18	8
CECONY | Earnings sharing - electric, gas and steam
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	10	15
CECONY | Settlement of prudence proceeding
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	7	8
CECONY | Other
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	188	163
CECONY | Refundable energy costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	8	12
CECONY | Deferred derivative gains
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	31	34
CECONY | Revenue decoupling mechanism
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	$ 0	$ 17