Note 13 - Retirement Fund and Profit Sharing Plan - Weighted Average Assumptions Used in Determining the Periodic Net Cost and Benefit Obligation (Details) - Supplemental Employee Retirement Plan [Member]	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Discount rate, net periodic benefit cost	3.00%	4.00%
Rate of compensation increase, net periodic benefit cost	2.50%	2.50%
Discount rate, benefit obligation	2.25%	3.00%
Rate of compensation increase, benefit obligation	2.50%	2.50%