Note 11 - Retirement Fund and Profit Sharing Plan - Components of SERP Expense (Details) - Supplemental Employee Retirement Plan [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Service cost	$ 169	$ 150	$ 339	$ 300
Interest cost	135	159	270	318
Net amortization	127	86	255	172
Net periodic benefit cost	$ 431	$ 395	$ 864	$ 790