Other Postretirement Benefits - Schedule of Actuarial Assumptions (Detail) - Other Postretirement Benefits	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets	7.75%	7.75%	7.75%
CECONY
Defined Benefit Plan Disclosure [Line Items]
Discount rate, benefit obligations	4.05%	3.75%	4.50%
Discount rate, net periodic benefit cost	3.75%	4.50%	3.75%
O&R
Defined Benefit Plan Disclosure [Line Items]
Discount rate, benefit obligations	4.20%	3.85%	4.75%
Discount rate, net periodic benefit cost	3.85%	4.75%	4.05%