Other Postretirement Benefits - Schedule of Change of Assumed Health Care Cost Trend Rate (Detail) (Scenario, Forecast [Member], Other Postretirement Benefits [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Schedule Of Other Postretirement Benefits [Line Items]
Effect on accumulated other postretirement benefit obligation, Increase	$ (12)
Effect on service cost and interest cost components for 2012, Increase
Effect on accumulated other postretirement benefit obligation, Decrease	12
Effect on service cost and interest cost components for 2012, Decrease
CECONY [Member]
Schedule Of Other Postretirement Benefits [Line Items]
Effect on accumulated other postretirement benefit obligation, Increase	(31)
Effect on service cost and interest cost components for 2012, Increase	(2)
Effect on accumulated other postretirement benefit obligation, Decrease	27
Effect on service cost and interest cost components for 2012, Decrease	$ 1