Income Tax - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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
Deferred tax asset, valuation allowance	$ 33,000,000	33,000,000	33,000,000
Decrease in uncertain tax positions resulting from settlement of claims filed in previous years		3,000,000	6,000,000	$ 0
Effective income tax rate reconciliation, uncertainty of taxes		4,000,000
Penalties for uncertain tax positions		0	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		6,000,000
New York State
Operating Loss Carryforwards [Line Items]
Decrease in effective tax rate resulting from tax settlement			6,000,000
Charitable Contribution
Operating Loss Carryforwards [Line Items]
Deferred tax asset, valuation allowance		0
General Business Tax Credit
Operating Loss Carryforwards [Line Items]
Tax credit carryovers		817,000,000
Expiring in 2020
Operating Loss Carryforwards [Line Items]
Charitable contribution carryforwards					$ 5,000,000
Expiring in 2021
Operating Loss Carryforwards [Line Items]
Charitable contribution carryforwards				5,000,000
Expiring in 2022
Operating Loss Carryforwards [Line Items]
Charitable contribution carryforwards	7,000,000		7,000,000
Expiring in 2023
Operating Loss Carryforwards [Line Items]
Charitable contribution carryforwards		5,000,000
Federal
Operating Loss Carryforwards [Line Items]
Additional depreciation deducted			477,000,000
Operating loss carryforwards	563,000,000	711,000,000	563,000,000
Operating loss carryover subject to expiration	520,000,000		520,000,000
Operating loss carryover not subject to expiration		191,000,000
State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, valuation allowance		21,000,000
State | New York State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	97,000,000	398,000,000	97,000,000
Operating loss carryforwards, valuation allowance		12,000,000
Decrease in uncertain tax positions resulting from settlement of claims filed in previous years			9,000,000
State | Carry Back to 2015 | New York State
Operating Loss Carryforwards [Line Items]
Income tax recovery resulting from operating loss carry back			9,000,000
State | Carry Back to 2015 and 2016 | New York State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		99,000,000
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		299,000,000
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	0
Decrease in uncertain tax positions resulting from settlement of claims filed in previous years		3,000,000	0	$ 0
Effective income tax rate reconciliation, uncertainty of taxes		2,000,000
Unrecognized tax benefits that would have an impact on effective tax rate		4,000,000
CECONY | New York State
Operating Loss Carryforwards [Line Items]
Decrease in uncertain tax positions resulting from settlement of claims filed in previous years			4,000,000
Decrease in effective tax rate resulting from tax settlement			1,000,000
CECONY | Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	153,000,000		153,000,000
CECONY | Future Income Tax
Operating Loss Carryforwards [Line Items]
Increase in regulatory liability resulting from TCJA	$ 3,513,000,000	49,000,000	3,513,000,000
CECONY | Accelerated Tax Depreciation Benefits
Operating Loss Carryforwards [Line Items]
Increase in regulatory liability resulting from TCJA		2,593,000,000	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