Regulatory Matters - Additional Information (Details) customer in Thousands, $ in Millions		1 Months Ended								3 Months Ended			9 Months Ended			12 Months Ended			13 Months Ended
	Apr. 01, 2018 USD ($)	Jan. 31, 2022 USD ($)	Jan. 31, 2021 USD ($)	Jan. 31, 2019 USD ($)	Nov. 30, 2018 USD ($)	Aug. 31, 2018 USD ($)	Mar. 31, 2018 USD ($) customer	Dec. 31, 2017 USD ($)	Apr. 30, 2017 USD ($)	Dec. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 31, 2022
Public Utilities, General Disclosures [Line Items]
Regulatory assets								$ 4,333.0		$ 4,370.0			$ 4,370.0		$ 4,333.0		$ 4,370.0	$ 4,333.0
Net benefit of the TCJA																		(259.0)
Regulatory liabilities								4,577.0		4,641.0			4,641.0		4,577.0		4,641.0	4,577.0
Utilities
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA																	434.0
Future Income Tax
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA																	54.0	3,713.0
Regulatory liabilities								2,545.0		2,515.0			2,515.0		2,545.0		2,515.0	2,545.0
Accelerated Tax Depreciation Benefits
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA																		2,684.0
Net Unbilled Revenue Deferrals
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities								183.0		117.0			117.0		$ 183.0		117.0	183.0
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%
Increase in regulatory liability resulting from TCJA							$ 28.0
Amount of customer refund to reflect TCJA					$ 0.6
Impact in regulatory liability resulting from TCJA, subject to normalization requirements							$ 16.0
RECO | NJBPU | Electric
Public Utilities, General Disclosures [Line Items]
Approved interim rate decrease	$ 2.9
Net benefit of the TCJA											$ 1.0
CECONY
Public Utilities, General Disclosures [Line Items]
Regulatory assets								3,925.0		3,987.0			3,987.0		$ 3,925.0		3,987.0	3,925.0
Regulatory liabilities								4,219.0		4,258.0			4,258.0		4,219.0		4,258.0	4,219.0
CECONY | Future Income Tax
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA								3,513.0									49.0	3,513.0
Regulatory liabilities								2,390.0		2,363.0			2,363.0		2,390.0		2,363.0	2,390.0
CECONY | Accelerated Tax Depreciation Benefits
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA																	2,593.0	2,542.0
CECONY | Deferred Income Tax Charge, Amortized Over Remaining Life of Asset
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA																	969.0
CECONY | Net Unbilled Revenue Deferrals
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities								183.0		117.0			117.0		$ 183.0		117.0	$ 183.0
CECONY | Electric | Hurricane
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer							209
Restoration costs													133.0
Operation and maintenance expenses													15.0
Operation and maintenance expenses charged against a storm reserve													83.0
Capital expenditures										29.0			29.0				29.0
Removal costs													6.0
CECONY | NYSPSC | Electric
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA						$ 2,516.0
Income tax benefit to be credited to customers resulting from TCJA										307.0
CECONY | NYSPSC | Gas
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA																	841.0
Income tax benefit to be credited to customers resulting from TCJA										90.0
CECONY | NYSPSC | Steam
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA																	$ 193.0
Income tax benefit to be credited to customers resulting from TCJA										6.0				$ 15.0
Tax credit, amortization period, protected portion																	3 years
CECONY | NYSPSC | MTA Subway Power Outage
Public Utilities, General Disclosures [Line Items]
Regulatory costs										260.0			260.0				$ 260.0
Regulatory assets										229.0			229.0				229.0
CECONY | NYSPSC | Scenario, Forecast | Electric
Public Utilities, General Disclosures [Line Items]
Income tax benefit to be credited to customers resulting from TCJA																$ 259.0
CECONY | NYSPSC | Scenario, Forecast | Gas
Public Utilities, General Disclosures [Line Items]
Income tax benefit to be credited to customers resulting from TCJA																113.0
CECONY | NYSPSC | Scenario, Forecast | Steam
Public Utilities, General Disclosures [Line Items]
Income tax benefit to be credited to customers resulting from TCJA																$ 25.0
CECONY | NYSPSC | Electric | MTA Subway Power Outage
Public Utilities, General Disclosures [Line Items]
Regulatory costs										31.0			31.0				31.0
CECONY | NYSPSC | Electric | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount		$ 263.0	$ 352.0
Return on common equity (percent)																			9.75%
Common equity ratio (percent)																			50.00%
CECONY | NYSPSC | Electric | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount				$ 485.0
Return on common equity (percent)				9.75%
Common equity ratio (percent)				50.00%
Proposed EAM (percent)				1.00%
CECONY | NYSPSC | Gas | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount		$ 155.0	$ 138.0
Return on common equity (percent)																			9.75%
Common equity ratio (percent)																			50.00%
CECONY | NYSPSC | Gas | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount				$ 210.0
Return on common equity (percent)				9.75%
Common equity ratio (percent)				50.00%
Proposed EAM (percent)				0.70%
O&R | Future Income Tax
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA								$ 161.0									2.0
O&R | Accelerated Tax Depreciation Benefits
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA																	128.0
O&R | Deferred Income Tax Charge, Amortized Over Remaining Life of Asset
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA																	$ 35.0
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 | NYSPSC | Electricity and Gas
Public Utilities, General Disclosures [Line Items]
Income tax benefit to be credited to customers resulting from TCJA										$ 22.0
Tax credit, amortization period, protected portion										3 years
Tax credit, amortization period, unprotected portion										15 years