Summary of Significant Accounting Policies - Changes in Accumulated Other Comprehensive Income by Component (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated OCI, net of taxes	$ (53)
OCI before reclassifications, net of tax of $15 and $1 for Con Edison and CECONY, respectively	21
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax of $5 and $1 for Con Edison and CECONY, respectively	7
TOTAL OTHER COMPREHENSIVE INCOME/(LOSS), NET OF TAXES	28	5	(18)
Accumulated OCI, net of taxes	(25)	(53)
CECONY [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated OCI, net of taxes	(9)
OCI before reclassifications, net of tax of $15 and $1 for Con Edison and CECONY, respectively	2
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax of $5 and $1 for Con Edison and CECONY, respectively	1
TOTAL OTHER COMPREHENSIVE INCOME/(LOSS), NET OF TAXES	3	(1)	(2)
Accumulated OCI, net of taxes	$ (6)	$ (9)