Regulatory Matters - Regulatory Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	$ 4,689	$ 4,827
Regulatory liabilities – current	123	102
Total Regulatory Liabilities	4,812	4,929
Future income tax
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	2,374	2,426
Allowance for cost of removal less salvage
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	1,007	989
TCJA net benefits
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	421	471
Net proceeds from sale of property
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	166	173
Energy efficiency portfolio standard unencumbered funds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	120	122
Net unbilled revenue deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	95	199
Pension and other postretirement benefit deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	65	75
System benefit charge carrying charge
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	53	48
Property tax refunds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	41	45
Unrecognized other postretirement costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	37	9
BQDM and REV Demo reconciliations
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	27	27
Settlement of gas proceedings
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	24	10
Sales and use tax refunds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	19	8
Earnings sharing - electric, gas and steam
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	18	22
Settlement of prudence proceeding
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	7	8
Other
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	215	195
Refundable energy costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	68	44
Deferred derivative gains
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	33	34
Revenue decoupling mechanism
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	22	24
CECONY
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	4,262	4,427
Regulatory liabilities – current	93	63
Total Regulatory Liabilities	4,355	4,490
CECONY | Future income tax
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	2,224	2,275
CECONY | Allowance for cost of removal less salvage
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	859	843
CECONY | TCJA net benefits
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	407	454
CECONY | Net proceeds from sale of property
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	166	173
CECONY | Energy efficiency portfolio standard unencumbered funds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	117	118
CECONY | Net unbilled revenue deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	95	199
CECONY | Pension and other postretirement benefit deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	35	46
CECONY | System benefit charge carrying charge
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	47	44
CECONY | Property tax refunds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	41	45
CECONY | Unrecognized other postretirement costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	3	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	24	10
CECONY | Sales and use tax refunds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	19	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	183	163
CECONY | Refundable energy costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	38	12
CECONY | Deferred derivative gains
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	33	34
CECONY | Revenue decoupling mechanism
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	$ 22	$ 17