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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Service cost	$ 144	$ 183	$ 432	$ 549
Interest cost	185	166	555	498
Net amortization	48	111	144	332
Net periodic benefit cost	$ 377	$ 460	$ 1,131	$ 1,379