Pension Benefits - Schedule of Assumptions (Detail) - Pension Benefits	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Discount rate, benefit obligations	4.25%	3.90%	4.80%
Discount rate, net periodic benefit cost	3.90%	4.80%	4.10%
Expected return on plan assets	7.80%	8.00%	8.00%
CECONY
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	4.25%	4.25%	4.35%
Rate of compensation increase	4.25%	4.35%	4.35%
O&R
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	4.00%	4.00%	4.25%
Rate of compensation increase	4.00%	4.25%	4.25%