Income Tax - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Decrease in net deferred tax liabilities resulting from TCJA		$ 13,000,000	$ 5,312,000,000
Change in net income resulting from TCJA			259,000,000
Charitable contribution carryforwards	$ 28,000,000
Deferred tax asset, valuation allowance	40,000,000	33,000,000
Decrease in uncertain tax positions resulting from settlement of claims filed in previous years	2,000,000	3,000,000	6,000,000
Effective income tax rate reconciliation, uncertainty of taxes	10,000,000
Penalties for uncertain tax positions	0	0
Amount of interest and penalties in their consolidated balance sheets	0	0
Unrecognized tax benefits that would have an impact on effective tax rate	13,000,000
Unrecognized tax benefits that would have an impact on effective tax rate, net of tax	12,000,000
General Business Tax Credit
Operating Loss Carryforwards [Line Items]
Tax credit carryovers	896,000,000
Operating loss carryforwards, valuation allowance	0
Tax Year 2015
Operating Loss Carryforwards [Line Items]
Charitable contribution carryforwards	5,000,000
Tax Year 2016
Operating Loss Carryforwards [Line Items]
Charitable contribution carryforwards	7,000,000
Tax Year 2017
Operating Loss Carryforwards [Line Items]
Charitable contribution carryforwards	5,000,000
Tax Year 2018
Operating Loss Carryforwards [Line Items]
Charitable contribution carryforwards	5,000,000
Tax Year 2019
Operating Loss Carryforwards [Line Items]
Charitable contribution carryforwards	6,000,000
Federal
Operating Loss Carryforwards [Line Items]
Additional depreciation deducted			477,000,000
Operating loss carryforwards	36,000,000		563,000,000
Operating loss carryover subject to expiration		13,000,000
Operating loss carryover not subject to expiration	23,000,000
State | New York State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		272,000,000
Operating loss carryforwards, valuation allowance	22,000,000
Decrease in uncertain tax positions resulting from settlement of claims filed in previous years	4,000,000
State | New York City
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, valuation allowance	18,000,000
State | Carry Back to 2015 and 2016 | New York State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	100,000,000
Income tax recovery resulting from operating loss carry back	9,000,000
State | Carried Forward to Future Years | New York State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	172,000,000
State | Tax Year 2019 | New York State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	453,000,000
Parent Company
Operating Loss Carryforwards [Line Items]
Change in net income resulting from TCJA		42,000,000	(21,000,000)
Clean Energy Businesses
Operating Loss Carryforwards [Line Items]
Change in net income resulting from TCJA			269,000,000
Con Edison Transmission
Operating Loss Carryforwards [Line Items]
Change in net income resulting from TCJA			11,000,000
Future Income Tax
Operating Loss Carryforwards [Line Items]
Increase in regulatory liability resulting from TCJA		54,000,000	3,713,000,000
Accelerated Tax Depreciation Benefits
Operating Loss Carryforwards [Line Items]
Increase in regulatory liability resulting from TCJA			2,684,000,000
Future Income Tax
Operating Loss Carryforwards [Line Items]
Decrease in regulatory asset resulting from TCJA			1,250,000,000
Revenue Taxes
Operating Loss Carryforwards [Line Items]
Decrease in regulatory asset resulting from TCJA			90,000,000
CECONY
Operating Loss Carryforwards [Line Items]
Decrease in net deferred tax liabilities resulting from TCJA		50,000,000	4,781,000,000
Deferred tax asset, valuation allowance	0	0
Decrease in uncertain tax positions resulting from settlement of claims filed in previous years	2,000,000	3,000,000	0
Effective income tax rate reconciliation, uncertainty of taxes	1,000,000
Unrecognized tax benefits that would have an impact on effective tax rate	2,000,000
CECONY | New York State
Operating Loss Carryforwards [Line Items]
Decrease in uncertain tax positions resulting from settlement of claims filed in previous years	$ 2,000,000
CECONY | Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards			153,000,000
CECONY | Future Income Tax
Operating Loss Carryforwards [Line Items]
Increase in regulatory liability resulting from TCJA		49,000,000	3,513,000,000
CECONY | Accelerated Tax Depreciation Benefits
Operating Loss Carryforwards [Line Items]
Increase in regulatory liability resulting from TCJA			2,542,000,000
CECONY | Future Income Tax
Operating Loss Carryforwards [Line Items]
Decrease in regulatory asset resulting from TCJA			1,182,000,000
CECONY | Revenue Taxes
Operating Loss Carryforwards [Line Items]
Decrease in regulatory asset resulting from TCJA		$ 1,000,000	$ 86,000,000