Environmental Matters - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Asbestos Proceedings [Member]
Site Contingency [Line Items]
Estimated undiscounted asbestos liability	$ 8
CECONY [Member] | Asbestos Proceedings [Member]
Site Contingency [Line Items]
Estimated undiscounted asbestos liability	7
Estimated undiscounted asbestos liability in year	15 years
CECONY [Member] | Superfund Sites [Member] | Manufactured Gas Plant Sites [Member]
Site Contingency [Line Items]
Estimated aggregate undiscounted potential liability related environmental contaminants	2,400
Orange and Rockland Utilities, Inc. [Member] | Superfund Sites [Member] | Manufactured Gas Plant Sites [Member]
Site Contingency [Line Items]
Estimated aggregate undiscounted potential liability related environmental contaminants	$ 167