Note 13 - Retirement Fund and Profit Sharing Plan - Components of SERP Expense (Details) - Supplemental Employee Retirement Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Service cost	$ 600	$ 576
Interest cost	636	739
Net amortization	343	192
Net periodic benefit cost	$ 1,579	$ 1,507