Note 10 - Employment Benefit and Retirement Plans - Components of Net Periodic Benefit Cost (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Director Retirement Plan [Member]
Service cost	$ 0	$ 0
Interest cost	12,000	12,000
Amortization net gain	(20,347)	(14,345)
Net benefit	(8,347)	(2,345)
Postretirement Health Coverage [Member]
Service cost		16,589
Interest cost		11,560
Amortization net gain		(40,096)
Net benefit		$ (11,947)