Environmental Matters - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Superfund Sites
Site Contingency [Line Items]
Remediation cost estimate	$ 55
Superfund Sites | Manufactured Gas Plant Sites | Maximum
Site Contingency [Line Items]
Estimated aggregate undiscounted potential liability related environmental contaminants (up to)	$ 2,800
CECONY | Asbestos Proceedings
Site Contingency [Line Items]
Estimated undiscounted asbestos liability (years)	15 years
CECONY | Superfund Sites
Site Contingency [Line Items]
Remediation cost estimate	$ 47
CECONY | Superfund Sites | Manufactured Gas Plant Sites | Maximum
Site Contingency [Line Items]
Estimated aggregate undiscounted potential liability related environmental contaminants (up to)	$ 2,600