Related Party Transactions - Additional Information (Details)	7 Months Ended	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($) agreement	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jan. 31, 2016
Related Party Transaction [Line Items]
Gas purchased for resale		$ 477,000,000	$ 495,000,000	$ 811,000,000
CECONY
Related Party Transaction [Line Items]
Sale of natural gas		47,000,000	54,000,000	80,000,000
Gas purchased for resale		319,000,000	337,000,000	$ 609,000,000
Funding limit of CECONY to O&R (not to exceed)		$ 250,000,000
CECONY | Related Party, Lending of Funds
Related Party Transaction [Line Items]
Lending period (not more than) (months)		12 months
CECONY | Equity Method Investee | Stagecoach | Purchased Power Costs
Related Party Transaction [Line Items]
Gas purchased for resale	$ 18,000,000
CECONY | Equity Method Investee | Stagecoach | Purchased Power Costs | Clean Energy Businesses
Related Party Transaction [Line Items]
Number of electricity sales agreements entered into | agreement		2
CET Electric
Related Party Transaction [Line Items]
Ownership interest, percentage	45.70%	45.70%			45.70%
O&R
Related Party Transaction [Line Items]
Outstanding loans to O&R		$ 0	$ 0