Note 3 - Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Securities, continuous unrealized loss position, less than 12 months, fair value	$ 31,789,015	$ 74,651,451
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(311,623)	(2,108,360)
Securities, continuous unrealized loss position, 12 months or more, fair value	31,682,639	4,709,778
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(744,180)	(108,845)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	63,471,654	79,361,229
Securities, continuous unrealized loss position, unrealized losses	(1,055,803)	(2,217,205)
Securities, continuous unrealized loss position, less than 12 months, fair value	31,789,015	74,651,451
Securities, continuous unrealized loss position, fair value	63,471,654	79,361,229
US States and Political Subdivisions Debt Securities [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	10,507,517	33,084,816
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(91,926)	(1,082,021)
Securities, continuous unrealized loss position, 12 months or more, fair value	10,671,807	179,402
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(237,065)	(3,633)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	21,179,324	33,264,218
Securities, continuous unrealized loss position, unrealized losses	(328,991)	(1,085,654)
Securities, continuous unrealized loss position, less than 12 months, fair value	10,507,517	33,084,816
Securities, continuous unrealized loss position, fair value	21,179,324	33,264,218
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	21,281,498	39,570,463
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(219,697)	(1,022,511)
Securities, continuous unrealized loss position, 12 months or more, fair value	21,010,832	3,649,276
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(507,115)	(104,526)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	42,292,330	43,219,739
Securities, continuous unrealized loss position, unrealized losses	(726,812)	(1,127,037)
Securities, continuous unrealized loss position, less than 12 months, fair value	21,281,498	39,570,463
Securities, continuous unrealized loss position, fair value	$ 42,292,330	43,219,739
Corporate Debt Securities [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value		1,996,172
Securities, continuous unrealized loss position, less than 12 months, unrealized losses		(3,828)
Securities, continuous unrealized loss position, 12 months or more, fair value		881,100
Securities, continuous unrealized loss position, 12 months or more, unrealized losses		(686)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		2,877,272
Securities, continuous unrealized loss position, unrealized losses		(4,514)
Securities, continuous unrealized loss position, less than 12 months, fair value		1,996,172
Securities, continuous unrealized loss position, fair value		$ 2,877,272