Pension and Other Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
General Discussion of Pension and Other Postretirement Benefits	The Company maintains a frozen noncontributory pension plan covering employees of the Company prior to the merger with Legacy ConnectOne. The benefits are based on years of service and the employee’s compensation over the prior five-year period. The plan’s benefits are payable in the form of a ten-year certain and life annuity. The plan is intended to be a tax-qualified defined benefit plan under Section 401(a) of the Internal Revenue Code. Payments may be made under the Pension Plan once attaining the normal retirement age of 65 and are generally equal to 44% of a participant’s highest average compensation over a 5-year period.
Defined Benefit Plan, Effect of Settlements and Curtailments on Accumulated Benefit Obligation	$ 13,500	$ 12,500
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax	3
Defined Benefit Plan, Contributions by Employer	$ 1,600	1,300	$ 900
Defined Benefit Plan, Description of Plan Amendment	Beginning with the 2014 plan year, the 401(k) plan was amended to provide for a match of 50% of elective contributions, up to 6% of an employee’s contribution. In 2018, the 401 (k) plan was amended to provide for 100% matching of employee contributions up to 5%
SERP compensation expense	$ 400	$ 300