Income Tax - Schedule of Income Tax Reconciliation (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Rate Reconciliation [Line Items]
Federal	35.00%	35.00%	35.00%
State income tax	4.00%	5.00%	5.00%
Cost of removal	(4.00%)	(4.00%)	(4.00%)
Other	(1.00%)		(1.00%)
Effective Tax Rate	34.00%	36.00%	35.00%
CECONY [Member]
Income Tax Rate Reconciliation [Line Items]
Federal	35.00%	35.00%	35.00%
State income tax	4.00%	5.00%	5.00%
Cost of removal	(4.00%)	(4.00%)	(4.00%)
Other	(1.00%)		(1.00%)
Effective Tax Rate	34.00%	36.00%	35.00%