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, 2019	Dec. 31, 2018
Service cost	$ 576	$ 732
Interest cost	739	664
Net amortization	192	443
Net periodic benefit cost	$ 1,507	$ 1,839