Related Party Transactions - Additional Information (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) MMBTU agreement	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 31, 2016
CECONY
Related Party Transaction [Line Items]
Net assets	$ 12,910,000,000
Sale of natural gas	83,000,000	$ 66,000,000	$ 47,000,000
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 | Mountain Valley Pipeline
Related Party Transaction [Line Items]
Amount of transaction	$ 0	0
Contract term (years)	20 years
Generating capacity per day (in dekatherms) | MMBTU	250,000
CECONY | Equity Method Investee | Stagecoach | Purchased Power Costs
Related Party Transaction [Line Items]
Amount of transaction	$ 28,000,000	31,000,000	$ 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
CECONY | Affiliated Entity | Financial Electric Capacity Contract | Con Edison Energy
Related Party Transaction [Line Items]
Gain (loss) on financial electric capacity contracts	$ (1,000,000)	3,000,000
O&R
Related Party Transaction [Line Items]
Net assets	712,000,000
Outstanding loans	$ 0	$ 0
CET Electric | NY Transco
Related Party Transaction [Line Items]
Ownership interest, percentage	45.70%
CET Gas | Mountain Valley Pipeline
Related Party Transaction [Line Items]
Percentage of equity interest owned	12.50%			12.50%