Regulatory Matters - Regulatory Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	$ 4,590	$ 4,641
Regulatory liabilities – current	93	114
Total Regulatory Liabilities	4,683	4,755
Future income tax
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	2,448	2,515
Allowance for cost of removal less salvage
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	952	928
TCJA net benefits
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	462	434
Net unbilled revenue deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	145	117
Energy efficiency portfolio standard unencumbered funds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	123	127
Pension and other postretirement benefit deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	67	62
Property tax refunds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	45	45
Net proceeds from sale of property
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	44	6
System benefit charge carrying charge
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	43	27
Earnings sharing - electric, gas and steam
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	26	36
BQDM and REV Demo reconciliations
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	25	18
Settlement of prudence proceeding
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	15	37
Settlement of gas proceedings
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	11	15
Unrecognized other postretirement costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	5	7
Carrying charges on repair allowance and bonus depreciation
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	4	21
New York State income tax rate change
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	3	17
Base rate change deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	1	10
Property tax reconciliation
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	0	36
Other
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	171	183
Refundable energy costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	36	31
Deferred derivative gains
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	33	30
Revenue decoupling mechanism
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	24	53
CECONY
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	4,200	4,258
Regulatory liabilities – current	56	73
Total Regulatory Liabilities	4,256	4,331
CECONY | Future income tax
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	2,302	2,363
CECONY | Allowance for cost of removal less salvage
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	808	790
CECONY | TCJA net benefits
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	444	411
CECONY | Net unbilled revenue deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	145	117
CECONY | Energy efficiency portfolio standard unencumbered funds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	119	122
CECONY | Pension and other postretirement benefit deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	41	40
CECONY | Property tax refunds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	45	45
CECONY | Net proceeds from sale of property
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	44	6
CECONY | System benefit charge carrying charge
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	38	24
CECONY | Earnings sharing - electric, gas and steam
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	19	27
CECONY | BQDM and REV Demo reconciliations
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	24	18
CECONY | Settlement of prudence proceeding
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	15	37
CECONY | Settlement of gas proceedings
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	11	15
CECONY | Unrecognized other postretirement costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	0	7
CECONY | Carrying charges on repair allowance and bonus depreciation
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	4	21
CECONY | New York State income tax rate change
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	3	17
CECONY | Base rate change deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	1	10
CECONY | Property tax reconciliation
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	0	36
CECONY | Other
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	137	152
CECONY | Refundable energy costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	8	8
CECONY | Deferred derivative gains
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	32	29
CECONY | Revenue decoupling mechanism
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	$ 16	$ 36