Note 3 - Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Securities, continuous unrealized loss position, less than 12 months, fair value	$ 13,452,347	$ 31,113,287
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(180,056)	(357,654)
Securities, continuous unrealized loss position, 12 months or more, fair value	56,982,249	30,994,373
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(1,767,993)	(814,880)
Securities, continuous unrealized loss position, fair value	70,434,596	62,107,660
Securities, continuous unrealized loss position, unrealized losses	(1,948,049)	(1,172,534)
US States and Political Subdivisions Debt Securities [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	6,324,750	11,024,593
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(67,774)	(103,747)
Securities, continuous unrealized loss position, 12 months or more, fair value	23,223,221	8,802,796
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(642,935)	(159,874)
Securities, continuous unrealized loss position, fair value	29,547,971	19,827,389
Securities, continuous unrealized loss position, unrealized losses	(710,709)	(263,621)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	7,127,597	20,088,694
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(112,282)	(253,907)
Securities, continuous unrealized loss position, 12 months or more, fair value	33,759,028	22,191,577
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(1,125,058)	(655,006)
Securities, continuous unrealized loss position, fair value	40,886,625	42,280,271
Securities, continuous unrealized loss position, unrealized losses	$ (1,237,340)	$ (908,913)