Note 3 - Investment Securities - Amortized Cost and Fair Value of Securities by Contractual Maturity (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Due in one year or less	$ 23,795,317
Due in one year or less	23,816,249
Due after one year through five years	16,362,018
Due after one year through five years	16,406,132
Due after five years	282,751,721
Due after five years	280,192,518
	322,909,056
	320,414,899	$ 255,691,285
Due in one year or less	3,103,329
Due in one year or less	3,102,013
Due after one year through five years	44,550,460
Due after one year through five years	44,614,611
Due after five years	51,444,058
Due after five years	50,971,409
	99,097,847
	98,688,033
	253,609,401
	251,113,139
Callable Securities [Member]
	45,091,138
	44,716,752
US States and Political Subdivisions Debt Securities [Member]
	319,364,899	254,641,285
US States and Political Subdivisions Debt Securities [Member] | Callable Securities [Member]
Amortized Cost	40,032,698
Fair Value	39,633,259
US Government-sponsored Enterprises Debt Securities [Member] | Callable Securities [Member]
Amortized Cost	5,058,440
Fair Value	5,083,493
Residential Mortgage Backed Securities [Member]
Amortized Cost	150,465,222
Fair Value	147,702,127
Other Securities [Member]
	1,050,000	$ 1,050,000
Amortized Cost	4,046,332
Fair Value	4,722,979
Callable Securities [Member] | US States and Political Subdivisions Debt Securities [Member]
Amortized Cost	179,399,031
Fair Value	$ 176,447,494