Regulatory Matters - Other Regulatory Matters (Details) customer in Thousands, $ in Thousands		1 Months Ended				3 Months Ended		9 Months Ended	12 Months Ended	36 Months Ended
	Jul. 13, 2019 USD ($) customer	Sep. 30, 2020 USD ($)	Aug. 31, 2020 USD ($) customer	Apr. 30, 2020 USD ($)	Mar. 31, 2018 customer	Mar. 31, 2020 USD ($)	Mar. 31, 2019	Sep. 30, 2020 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2022 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
CECONY | NYSPSC | Manhattan Steam Main Rupture
Public Utilities, General Disclosures [Line Items]
Property damage, clean up and response expense								$ 17,000
Capital and retirement costs								9,000
Loss contingency accrual											$ 3,000
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 | Electric
Public Utilities, General Disclosures [Line Items]
Revenues, negative adjustment		$ 5,000
CECONY | Electric | West Side of Manhattan
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer	72
Revenues, negative adjustment	$ 5,000
CECONY | Electric | Brooklyn
Public Utilities, General Disclosures [Line Items]
Revenues, negative adjustment	$ 10,000
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
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer			330
Restoration costs								142,000
Operation and maintenance expenses								13,000
Operation and maintenance expenses charged against a storm reserve								73,000
Capital expenditures		56,000						56,000
Loss contingency accrual		5,000						5,000
CECONY | Electric | NYSPSC | Hurricane
Public Utilities, General Disclosures [Line Items]
Loss contingency accrual											5,600
Settlement agreement, amount awarded for the benefit			$ 5,600
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]
Impact 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
Impact in regulatory liability resulting from TCJA										$ 784,000
CECONY | Gas | NYSPSC | Violations of Gas Operator Qualification, Performance and Inspection Requirements
Public Utilities, General Disclosures [Line Items]
Loss contingency accrual						5,000						$ 10,000
Settlement agreement, amount				$ 15,000
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]
Impact 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
Impact in regulatory liability resulting from TCJA										$ 107,000
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
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer			200
Restoration costs								30,000
Operation and maintenance expenses charged against a storm reserve								23,000
Capital expenditures		7,000						7,000
Loss contingency accrual		$ 2,000						$ 2,000
O&R | Electric | NYSPSC | Hurricane
Public Utilities, General Disclosures [Line Items]
Loss contingency accrual											$ 850
Settlement agreement, amount awarded for the benefit			$ 850
O&R | Electric and Gas Transmission Projects | 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 Transmission Projects | Scenario, Forecast | Protected Portion
Public Utilities, General Disclosures [Line Items]
Impact in regulatory liability resulting from TCJA										$ 123,000
O&R | Electric and Gas Transmission Projects | Scenario, Forecast | Unprotected Portion
Public Utilities, General Disclosures [Line Items]
TCJA, net benefit amortization, allocation period										15 years
Impact in regulatory liability resulting from TCJA										$ 30,000
RECO | Electric | Hurricane
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer					44
Restoration costs						$ 17,000