Regulatory Matters - Additional Information (Details) customer in Thousands, $ in Thousands		1 Months Ended				3 Months Ended	9 Months Ended	12 Months Ended			36 Months Ended
	Jul. 13, 2019 customer	Nov. 30, 2020 USD ($) claim	Aug. 31, 2020 USD ($) customer	Mar. 31, 2018 customer	Apr. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2017	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2022 USD ($)	Jun. 30, 2020 USD ($)	Apr. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jul. 31, 2019 USD ($)
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities								$ 4,513,000	$ 4,827,000
Return On regulatory assets								$ 1,696,000	$ 1,188,000
Other Customer-Provided Capital rate								2.65%	4.20%
Future Income Tax
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities								$ 2,207,000	$ 2,426,000
Net Unbilled Revenue Deferrals
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities								198,000	199,000
RECO | Electric | Hurricane
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer				44
Restoration costs								17,000
RECO | FERC
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount					$ 17,700	$ 11,800
Return on common equity (percent)							10.00%
CECONY
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities								4,094,000	4,427,000
Return On regulatory assets								1,509,000	1,054,000
CECONY | Future Income Tax
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities								2,062,000	2,275,000
CECONY | Net Unbilled Revenue Deferrals
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities								198,000	199,000
CECONY | Electric | Hurricane
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer				209
Restoration costs								134,000
Operation and maintenance expenses								15,000
Operation and maintenance expenses charged against a storm reserve								84,000
Capital expenditures								29,000
Removal costs								6,000
CECONY | Electric | Tropical Storm [Member]
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer			330
Restoration costs								153,000
Operation and maintenance expenses								18,000
Operation and maintenance expenses charged against a storm reserve								77,000
Capital expenditures								58,000
Property damage, clean up and response costs								7,500
Estimate of possible loss		$ 102,300
Alleged number of claims, violations | claim		33
CECONY | Electric | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Income tax benefit to be credited to customers resulting from TCJA											$ 377,000
TCJA, net benefit amortization, allocation period											3 years
CECONY | Electric | Scenario, Forecast | Protected Portion
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA											$ 1,663,000
CECONY | Electric | Scenario, Forecast | Unprotected Portion
Public Utilities, General Disclosures [Line Items]
TCJA, net benefit amortization, allocation period											5 years
Increase in regulatory liability resulting from TCJA											$ 784,000
CECONY | Gas | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Income tax benefit to be credited to customers resulting from TCJA											$ 63,000
TCJA, net benefit amortization, allocation period											2 years
CECONY | Gas | Scenario, Forecast | Protected Portion
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA											$ 725,000
CECONY | Gas | Scenario, Forecast | Unprotected Portion
Public Utilities, General Disclosures [Line Items]
TCJA, net benefit amortization, allocation period											5 years
Increase in regulatory liability resulting from TCJA											$ 107,000
CECONY | NYSPSC | Steam
Public Utilities, General Disclosures [Line Items]
Income tax benefit to be credited to customers resulting from TCJA								$ 185,000		$ 15,000
Tax credit, amortization period								3 years
CECONY | NYSPSC | Electric | Hurricane
Public Utilities, General Disclosures [Line Items]
Loss contingency accrual								$ 5,600
Settlement agreement amount			$ 5,600
O&R | Electric | Hurricane
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer				93
Restoration costs								43,000
O&R | Electric | Tropical Storm [Member]
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer			200
Restoration costs								34,000
Operation and maintenance expenses charged against a storm reserve								26,000
Capital expenditures								8,000
Property damage, clean up and response costs								2,900
Estimate of possible loss		$ 19,000
Alleged number of claims, violations | claim		38
O&R | Electric and Gas | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Income tax benefit to be credited to customers resulting from TCJA											$ 22,000
TCJA, net benefit amortization, allocation period											3 years
O&R | Electric and Gas | Scenario, Forecast | Protected Portion
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA											$ 123,000
O&R | Electric and Gas | Scenario, Forecast | Unprotected Portion
Public Utilities, General Disclosures [Line Items]
TCJA, net benefit amortization, allocation period											15 years
Increase in regulatory liability resulting from TCJA											$ 30,000
O&R | NYSPSC | Electric | Hurricane
Public Utilities, General Disclosures [Line Items]
Loss contingency accrual								$ 850
Settlement agreement amount			$ 850
Manhattan | CECONY | Electric
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer	72
Estimate of possible loss															$ 24,800
Brooklyn | CECONY | Electric
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer	30
Cumulative catch-up adjustment to revenue, modification of contract									(15,000)
Manhattan Steam Main Rupture | CECONY | NYSPSC
Public Utilities, General Disclosures [Line Items]
Property damage, clean up and response costs									17,000
Capital and retirement costs									9,000
Loss contingency accrual												$ 3,000	$ 15,000
Violations Of Gas Operator Qualification, Performance, And Inspection Requirements | CECONY | NYSPSC | Gas
Public Utilities, General Disclosures [Line Items]
Loss contingency accrual									$ 10,000					$ 5,000