Other Postretirement Benefits - Schedule of Actuarial Assumptions (Detail) (Other Postretirement Benefits [Member])	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule Of Other Postretirement Benefits [Line Items]
Discount rate, net periodic benefit	4.55%	5.40%	5.95%
Expected return on plan assets	8.50%	8.50%	8.50%
CECONY [Member]
Schedule Of Other Postretirement Benefits [Line Items]
Discount rate, benefit obligations	3.75%	4.55%	5.40%
O&R [Member]
Schedule Of Other Postretirement Benefits [Line Items]
Discount rate, benefit obligations	4.05%	4.55%	5.40%