Regulatory Matters - Other Regulatory Matters (Details) customer in Thousands, $ in Millions		1 Months Ended	3 Months Ended				6 Months Ended		9 Months Ended	12 Months Ended		15 Months Ended
	Jul. 13, 2019 customer	Mar. 31, 2018 customer	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2019 USD ($)
Public Utilities, General Disclosures [Line Items]
Regulatory assets				$ 4,334	$ 4,370		$ 4,334				$ 4,370	$ 4,334
Revenues				(2,744)		$ (2,696)	(6,258)	$ (6,060)
Electric
Public Utilities, General Disclosures [Line Items]
Revenues				(1,971)		(1,951)	(3,912)	(3,828)
Gas
Public Utilities, General Disclosures [Line Items]
Revenues				(449)		(489)	(1,484)	(1,428)
Steam
Public Utilities, General Disclosures [Line Items]
Revenues				(90)		(96)	(411)	(410)
CECONY
Public Utilities, General Disclosures [Line Items]
Regulatory assets				3,976	3,987		3,976				$ 3,987	3,976
Revenues				(2,331)		(2,338)	(5,371)	(5,222)
CECONY | Electric
Public Utilities, General Disclosures [Line Items]
Revenues				(1,833)		(1,807)	(3,630)	(3,536)
CECONY | Gas
Public Utilities, General Disclosures [Line Items]
Revenues				(408)		(435)	(1,330)	(1,276)
CECONY | Steam
Public Utilities, General Disclosures [Line Items]
Revenues				(90)		$ (96)	(411)	$ (410)
CECONY | Electric | Subsequent Event | West Side of Manhattan
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer	72
CECONY | Electric | Hurricane
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer		209
Restoration costs												134
Operation and maintenance expenses												15
Operation and maintenance expenses charged against a storm reserve												84
Capital expenditures				29			29					29
Removal costs												6
CECONY | Electric | Scenario, Forecast | Subsequent Event | West Side of Manhattan
Public Utilities, General Disclosures [Line Items]
Revenues			$ 5
O&R | Electric | Hurricane
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer		93
Restoration costs												43
RECO | Electric | Hurricane
Public Utilities, General Disclosures [Line Items]
Number of customers affected with interrupted service | customer		44
Restoration costs												17
NYSPSC | CECONY | Electric
Public Utilities, General Disclosures [Line Items]
Income tax benefit to be credited to customers resulting from TCJA					311
Impact in regulatory liability resulting from TCJA							2,489
NYSPSC | CECONY | Electric | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Income tax benefit to be credited to customers resulting from TCJA										$ 259
NYSPSC | CECONY | Gas
Public Utilities, General Disclosures [Line Items]
Income tax benefit to be credited to customers resulting from TCJA					$ 90
Impact in regulatory liability resulting from TCJA							804
NYSPSC | CECONY | Gas | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Income tax benefit to be credited to customers resulting from TCJA										113
NYSPSC | CECONY | Steam
Public Utilities, General Disclosures [Line Items]
Income tax benefit to be credited to customers resulting from TCJA									$ 15
Tax credit, amortization period											3 years
Impact in regulatory liability resulting from TCJA							185
NYSPSC | CECONY | Steam | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Income tax benefit to be credited to customers resulting from TCJA										$ 25
NYSPSC | CECONY | MTA Subway Power Outage
Public Utilities, General Disclosures [Line Items]
Regulatory costs				273			273					273
Regulatory assets				241			241					241
NYSPSC | CECONY | MTA Subway Power Outage | Electric
Public Utilities, General Disclosures [Line Items]
Regulatory costs				$ 32			$ 32					$ 32