Note 1 - Summary of Significant Accounting Policies - Accumulated Other Comprehensive Earnings (Details) - USD ($)		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Balance		$ 66,341,834	$ 58,593,299
Balance		68,032,876	62,941,961
Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2016-01 [Member]
Balance	[1]
AOCI Attributable to Parent [Member]
Balance		2,953,936	(1,580,976)
Other comprehensive earnings before reclassification		2,579,925	3,611,573
Amount reclassified from accumulated other comprehensive earnings		(325,204)	(188,340)
Net current period other comprehensive earnings		2,254,721	3,423,233
Balance		5,208,657	3,208,554
AOCI Attributable to Parent [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2016-01 [Member]
Balance			1,366,297	[1]
AOCI Attributable to Parent [Member] | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Balance		$ 2,953,936	$ (214,679)

[1] See discussion of Accounting Standards Update 2016-01 adoption in 2019 10-K, Note 1 - Summary of Significant Accounting Policies