Regulatory Matters - Additional Information (Details) customer in Thousands, $ in Millions		1 Months Ended			3 Months Ended	9 Months Ended		12 Months Ended			36 Months Ended
	Jul. 13, 2019 USD ($) customer	Jan. 31, 2019	Mar. 31, 2018 customer	Apr. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2022 USD ($)
Public Utilities, General Disclosures [Line Items]
Regulatory assets								$ 4,987.0	$ 4,370.0
Regulatory liabilities								4,827.0	4,641.0
Future Income Tax
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA									54.0	$ 3,713.0
Regulatory liabilities								2,426.0	2,515.0
Net Unbilled Revenue Deferrals
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities								199.0	117.0
RECO | Electric | Hurricane
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer			44
Restoration costs								17.0
RECO | FERC
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount				$ 17.7	$ 11.8
Return on common equity (percent)							10.00%
CECONY
Public Utilities, General Disclosures [Line Items]
Regulatory assets								4,600.0	3,987.0
Regulatory liabilities								4,427.0	4,258.0
CECONY | Future Income Tax
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA									49.0	$ 3,513.0
Regulatory liabilities								2,275.0	2,363.0
CECONY | Net Unbilled Revenue Deferrals
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities								199.0	$ 117.0
CECONY | Electric | Hurricane
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer			209
Restoration costs								134.0
Operation and maintenance expenses								15.0
Operation and maintenance expenses charged against a storm reserve								84.0
Capital expenditures								29.0
Removal costs								6.0
CECONY | Electric | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Tax Cuts And Jobs Act Of 2017, Net Benefit Amortization, Allocation Period											3 years
Income tax benefit to be credited to customers resulting from TCJA											$ 377.0
CECONY | Electric | Scenario, Forecast | Protected Portion
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA											$ 1,663.0
CECONY | Electric | Scenario, Forecast | Unprotected Portion
Public Utilities, General Disclosures [Line Items]
Tax Cuts And Jobs Act Of 2017, Net Benefit Amortization, Allocation Period											5 years
Increase in regulatory liability resulting from TCJA											$ 784.0
CECONY | Gas | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Tax Cuts And Jobs Act Of 2017, Net Benefit Amortization, Allocation Period											2 years
Income tax benefit to be credited to customers resulting from TCJA											$ 63.0
CECONY | Gas | Scenario, Forecast | Protected Portion
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA											$ 725.0
CECONY | Gas | Scenario, Forecast | Unprotected Portion
Public Utilities, General Disclosures [Line Items]
Tax Cuts And Jobs Act Of 2017, Net Benefit Amortization, Allocation Period											5 years
Increase in regulatory liability resulting from TCJA											$ 107.0
CECONY | NYSPSC | Steam
Public Utilities, General Disclosures [Line Items]
Tax Cuts And Jobs Act Of 2017, Net Benefit Amortization, Allocation Period						3 years
Income tax benefit to be credited to customers resulting from TCJA						$ 15.0		185.0
CECONY | NYSPSC | Electric
Public Utilities, General Disclosures [Line Items]
Proposed EAM (percent)		1.00%
CECONY | NYSPSC | Gas
Public Utilities, General Disclosures [Line Items]
Proposed EAM (percent)		0.70%
O&R | Electric | Hurricane
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer			93
Restoration costs								43.0
O&R | Electric and Gas | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Tax Cuts And Jobs Act Of 2017, Net Benefit Amortization, Allocation Period											3 years
Income tax benefit to be credited to customers resulting from TCJA											$ 22.0
O&R | Electric and Gas | Scenario, Forecast | Protected Portion
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA											$ 123.0
O&R | Electric and Gas | Scenario, Forecast | Unprotected Portion
Public Utilities, General Disclosures [Line Items]
Tax Cuts And Jobs Act Of 2017, Net Benefit Amortization, Allocation Period											15 years
Increase in regulatory liability resulting from TCJA											$ 30.0
Manhattan | CECONY | Electric
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer	72
Cumulative catch-up adjustment to revenue, modification of contract	$ (5.0)
Brooklyn | CECONY | Electric
Public Utilities, General Disclosures [Line Items]
Cumulative catch-up adjustment to revenue, modification of contract	$ (10.0)
Manhattan Steam Main Rupture | CECONY | NYSPSC
Public Utilities, General Disclosures [Line Items]
Property damage, clean up and response costs								17.0
Capital and retirement costs								9.0
Violations Of Gas Operator Qualification, Performance, And Inspection Requirements | CECONY | NYSPSC | Gas
Public Utilities, General Disclosures [Line Items]
Loss contingency accrual								$ 10.0