Note 3 - Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Securities, continuous unrealized loss position, less than 12 months, fair value	$ 38,829,962	$ 31,113,287
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(981,590)	(357,654)
Securities, continuous unrealized loss position, 12 months or more, fair value	29,652,326	30,994,373
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(1,247,395)	(814,880)
Securities, continuous unrealized loss position, fair value	68,482,288	62,107,660
Securities, continuous unrealized loss position, unrealized losses	(2,228,985)	(1,172,534)
US States and Political Subdivisions Debt Securities [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	19,061,837	11,024,593
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(483,654)	(103,747)
Securities, continuous unrealized loss position, 12 months or more, fair value	8,559,989	8,802,796
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(375,277)	(159,874)
Securities, continuous unrealized loss position, fair value	27,621,826	19,827,389
Securities, continuous unrealized loss position, unrealized losses	(858,931)	(263,621)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	19,768,125	20,088,694
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(497,936)	(253,907)
Securities, continuous unrealized loss position, 12 months or more, fair value	21,092,337	22,191,577
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(872,118)	(655,006)
Securities, continuous unrealized loss position, fair value	40,860,462	42,280,271
Securities, continuous unrealized loss position, unrealized losses	$ (1,370,054)	$ (908,913)