Note 11 - Retirement Fund and Profit Sharing Plan - Components of SERP Expense (Details) - Supplemental Employee Retirement Plan [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Service cost	$ 169	$ 150	$ 508	$ 450
Interest cost	135	159	405	477
Net amortization	127	86	382	258
Net periodic benefit cost	$ 431	$ 395	$ 1,295	$ 1,185