Stock-Based Compensation - Summary of Status of Stock Options Awarded (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding Shares, Beginning Balance	606,475
Exercised, Shares	(123,165)
Forfeited, Shares	(2,000)
Outstanding Shares, Ending Balance	481,310
Weighted Average Exercise Price Outstanding, Beginning Balance	$ 43.008
Weighted Average Exercise Price, Exercised	$ 41.539
Weighted Average Exercise Price, Forfeited	$ 43.170
Weighted Average Exercise Price Outstanding, Ending Balance	$ 43.383
CECONY [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding Shares, Beginning Balance	481,175
Exercised, Shares	(98,165)
Forfeited, Shares	(2,000)
Outstanding Shares, Ending Balance	381,010
Weighted Average Exercise Price Outstanding, Beginning Balance	$ 42.973
Weighted Average Exercise Price, Exercised	$ 41.553
Weighted Average Exercise Price, Forfeited	$ 43.170
Weighted Average Exercise Price Outstanding, Ending Balance	$ 43.338