Pension Benefits - Schedule of Employer Contribution to Defined Savings Plan (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Employer contribution to the defined savings plan	$ 887	$ 870	$ 628
Con Edison [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contribution to the defined savings plan	30	23	23
CECONY [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contribution to the defined savings plan	$ 830	$ 804	$ 576