Environmental Matters - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Site Contingency [Line Items]
Insurance recoveries	$ 0	$ 0
CECONY
Site Contingency [Line Items]
Insurance recoveries	$ 0	$ 0
CECONY | Asbestos Proceedings
Site Contingency [Line Items]
Estimated undiscounted asbestos liability (years)	15 years
Superfund Sites | Manufactured Gas Plant Sites | Maximum
Site Contingency [Line Items]
Estimated aggregate undiscounted potential liability related environmental contaminants (up to)			$ 2,700
Superfund Sites | Manufactured Gas Plant Sites | Maximum | CECONY
Site Contingency [Line Items]
Estimated aggregate undiscounted potential liability related environmental contaminants (up to)			$ 2,500