Note 13 - Income Taxes - The Provision for Income Taxes (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Taxes currently payable									$ 1,230,427	$ 1,490,297	$ 1,889,673
Deferred income taxes									624,386	68,340	123,091
Deferred income taxes related to 2017 Tax Act										1,012,112
	$ 624,023	$ 1,390,673	$ (453,574)	$ 293,691	$ 1,102,883	$ 443,651	$ 520,770	$ 503,445	$ 1,854,813	$ 2,570,749	$ 2,012,764