Regulatory Matters - Summary of Utilities Rate Plans (CECONY-Electric) (Details) - USD ($)	1 Months Ended	12 Months Ended			36 Months Ended
	Dec. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2022	Dec. 31, 2019	Dec. 31, 2016
Public Utilities, General Disclosures [Line Items]
Revenues		$ 12,574,000,000	$ 12,337,000,000	$ 12,033,000,000
Deferred revenues		17,000,000	20,000,000	87,000,000		$ 17,000,000
Deferred revenues		$ (599,000,000)	(514,000,000)			$ (599,000,000)
NYSPSC
Public Utilities, General Disclosures [Line Items]
Percentage of total consolidated revenues		15.00%				15.00%
Maximum | NYSPSC
Public Utilities, General Disclosures [Line Items]
Percentage of total consolidated revenues		15.00%				15.00%
Percentage of debt to total consolidated debt		20.00%
CECONY
Public Utilities, General Disclosures [Line Items]
Revenues		$ 10,821,000,000	10,680,000,000	10,468,000,000
Deferred revenues		(477,000,000)	(392,000,000)			$ (477,000,000)
CECONY | Electric
Public Utilities, General Disclosures [Line Items]
Retention of annual transmission congestion revenues						75,000,000
Actual earnings adjustment mechanism incentives		0	0	0
Other earnings incentives		0	0	0
Deferred revenues		69,000,000	(6,000,000)	45,000,000		69,000,000
Negative revenue adjustments		15,000,000	0	0
Cost reconciliation, deferred net regulatory liabilities		10,000,000	189,000,000	35,000,000		10,000,000
Deferred regulatory asset (liability)		(11,800,000)	(400,000)	400,000		$ (11,800,000)
Earnings sharing, threshold limit		$ 0	0
Earnings sharing, positive adjustment				$ 5,700,000
Common equity ratio (percent)						48.00%
Increase in gas base rate due to expiration of temporary credit under the prior rate plan	$ 48,000,000
Recovery or refund of energy costs, deferral period						10 years
Deferrals for property taxes limitation from rates (percent)							90.00%
Recovery deferral (percent)		80.00%				80.00%
Maximum deferral (percent)		30.00%				30.00%
CECONY | Electric | NYSPSC
Public Utilities, General Disclosures [Line Items]
Base rate changes		$ 199,000,000				$ 199,000,000
CECONY | Electric | Service Termination
Public Utilities, General Disclosures [Line Items]
Revenues		0	$ 0
CECONY | Electric | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Retention of annual transmission congestion revenues					$ 75,000,000
Authorized return on common equity (percent)					8.80%
Earnings sharing (percent)					9.30%
Common equity ratio (percent)					48.00%
Maximum deferral (percent)					15.00%
Income tax benefit to be credited to customers resulting from TCJA					$ 377,000,000
CECONY | Electric | Scenario, Forecast | Deferred Project Costs
Public Utilities, General Disclosures [Line Items]
Amortization to income of net regulatory (assets) and liabilities					238,000,000
CECONY | Electric | Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes		$ 195,000,000				195,000,000
Amortization to income of net regulatory (assets) and liabilities						84,000,000
Potential earnings adjustment mechanism incentives						0
Average rate base						$ 18,902,000,000
Weighted average cost of capital (after-tax) (percent)						6.82%
Authorized return on common equity (percent)						9.00%
Actual return on common equity (percent)						9.30%
Earnings sharing (percent)		9.50%				9.50%
Cost of long-term debt (percent)		4.93%				4.93%
Recovery of energy efficiency and savings program costs						$ 20,500,000
Deferral, annual maximum (not more than) (percent)							10.00%
CECONY | Electric | Year 1 | Electric average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations						21,689,000,000
CECONY | Electric | Year 1 | Advanced metering infrastructure (AMI)
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations						126,000,000
CECONY | Electric | Year 1 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)						376,000,000
CECONY | Electric | Year 1 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes					113,000,000
Amortization to income of net regulatory (assets) and liabilities					267,000,000
Potential earnings adjustment mechanism incentives					69,000,000
Potential penalties (annually)					450,000,000
Average rate base					$ 21,660,000,000
Weighted average cost of capital (after-tax) (percent)					6.82%
Cost of long-term debt (percent)					4.63%
Amount of cost recovery					$ 206,000,000
CECONY | Electric | Year 1 | Scenario, Forecast | Electric average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations					24,491,000,000
CECONY | Electric | Year 1 | Scenario, Forecast | Advanced metering infrastructure (AMI)
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations					572,000,000
CECONY | Electric | Year 2
Public Utilities, General Disclosures [Line Items]
Base rate changes		$ 155,000,000				155,000,000
Amortization to income of net regulatory (assets) and liabilities						83,000,000
Potential earnings adjustment mechanism incentives						0
Average rate base						$ 19,530,000,000
Weighted average cost of capital (after-tax) (percent)						6.80%
Actual return on common equity (percent)						9.36%
Cost of long-term debt (percent)		4.88%				4.88%
Recovery of energy efficiency and savings program costs						$ 49,000,000
Deferral, annual maximum (not more than) (percent)							0.075%
CECONY | Electric | Year 2 | Electric average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations						22,338,000,000
CECONY | Electric | Year 2 | Advanced metering infrastructure (AMI)
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations						257,000,000
CECONY | Electric | Year 2 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)						341,000,000
CECONY | Electric | Year 2 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes					370,000,000
Amortization to income of net regulatory (assets) and liabilities					269,000,000
Potential earnings adjustment mechanism incentives					74,000,000
Potential penalties (annually)					461,000,000
Average rate base					22,783,000,000
Amount of cost recovery					245,000,000
CECONY | Electric | Year 2 | Scenario, Forecast | Electric average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations					25,092,000,000
CECONY | Electric | Year 2 | Scenario, Forecast | Advanced metering infrastructure (AMI)
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations					740,000,000
CECONY | Electric | Year 3
Public Utilities, General Disclosures [Line Items]
Base rate changes		$ 155,000,000				155,000,000
Amortization to income of net regulatory (assets) and liabilities						69,000,000
Potential earnings adjustment mechanism incentives						0
Average rate base						$ 20,277,000,000
Weighted average cost of capital (after-tax) (percent)						6.73%
Actual return on common equity (percent)						8.82%
Cost of long-term debt (percent)		4.74%				4.74%
Recovery of energy efficiency and savings program costs						$ 107,500,000
Deferral, annual maximum (not more than) (percent)							0.05%
CECONY | Electric | Year 3 | Electric average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations						23,002,000,000
CECONY | Electric | Year 3 | Advanced metering infrastructure (AMI)
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations						415,000,000
CECONY | Electric | Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)						$ 352,000,000
CECONY | Electric | Year 3 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes					326,000,000
Amortization to income of net regulatory (assets) and liabilities					272,000,000
Potential earnings adjustment mechanism incentives					79,000,000
Potential penalties (annually)					476,000,000
Average rate base					23,926,000,000
Amount of cost recovery					251,000,000
CECONY | Electric | Year 3 | Scenario, Forecast | Electric average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations					25,708,000,000
CECONY | Electric | Year 3 | Scenario, Forecast | Advanced metering infrastructure (AMI)
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations					806,000,000
Annually | CECONY | Electric | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Income tax benefit to be credited to customers resulting from TCJA					126,000,000
Annually | CECONY | Electric | Scenario, Forecast | Deferred Project Costs
Public Utilities, General Disclosures [Line Items]
Amortization to income of net regulatory (assets) and liabilities					48,000,000
Protected Portion | CECONY | Electric | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA					(1,663,000,000)
Protected Portion | CECONY | Electric | Year 1 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA					(49,000,000)
Protected Portion | CECONY | Electric | Year 2 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA					(50,000,000)
Protected Portion | CECONY | Electric | Year 3 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA					(53,000,000)
Unprotected Portion | CECONY | Electric | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA					$ (784,000,000)
TCJA of 2017 regulatory liabilities, income tax benefit, amortization period					5 years
Unprotected Portion | Annually | CECONY | Electric | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA					$ (157,000,000)