Environmental Matters - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Site Contingency [Line Items]
Insurance recoveries	$ 0	$ 0
Manufactured gas plant sites | Maximum
Site Contingency [Line Items]
Estimated aggregate undiscounted potential liability related environmental contaminants (up to)			$ 2,800,000,000
CECONY
Site Contingency [Line Items]
Insurance recoveries	$ 0	$ 0
CECONY | Manufactured gas plant sites | Maximum
Site Contingency [Line Items]
Estimated aggregate undiscounted potential liability related environmental contaminants (up to)			$ 2,700,000,000
Asbestos Related
Site Contingency [Line Items]
Estimated undiscounted asbestos liability (years)	15 years
Asbestos Related | CECONY
Site Contingency [Line Items]
Estimated undiscounted asbestos liability (years)	15 years