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Environmental Matters - Additional Information (Details) - USD ($)
$ in Billions
 9 Months Ended
Sep. 30, 2019
Dec. 31, 2018
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)   $ 2.8
Superfund Sites | Manufactured Gas Plant Sites | Maximum | CECONY    
Site Contingency [Line Items]    
Estimated aggregate undiscounted potential liability related environmental contaminants (up to)   $ 2.6