Note 2 - Investment Securities - Amortized Cost and Fair Value of Securities by Contractual Maturity (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Due in one year or less	$ 7,479,990
Due in one year or less	7,478,528
Due after one year through five years	18,040,753
Due after one year through five years	18,137,483
Due after five years	298,682,891
Due after five years	297,373,366
	324,203,634
	322,989,377	$ 320,414,899
Due in one year or less	3,498,188
Due in one year or less	3,504,089
Due after one year through five years	31,550,278
Due after one year through five years	31,700,139
Due after five years	64,870,032
Due after five years	64,840,746
	99,918,498
	100,044,974
	270,047,939
	269,281,713
Callable Securities [Member]
	46,183,946
	46,135,385
US States and Political Subdivisions Debt Securities [Member]
	321,939,377	319,364,899
US States and Political Subdivisions Debt Securities [Member] | Callable Securities [Member]
Amortized Cost	41,135,349
Fair Value	41,095,251
US Government-sponsored Enterprises Debt Securities [Member] | Callable Securities [Member]
Amortized Cost	5,048,597
Fair Value	5,040,134
Residential Mortgage Backed Securities [Member]
Amortized Cost	166,063,973
Fair Value	164,414,833
Other Securities [Member]
	1,050,000	$ 1,050,000
Amortized Cost	4,065,468
Fair Value	4,821,906
Callable Securities [Member] | US States and Political Subdivisions Debt Securities [Member]
Amortized Cost	170,556,294
Fair Value	$ 170,715,228