Note 4 - Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Securities, continuous unrealized loss position, less than 12 months, fair value	$ 8,313,305	$ 13,452,347
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(62,002)	(180,056)
Securities, continuous unrealized loss position, 12 months or more, fair value	45,454,055	56,982,249
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(722,769)	(1,767,913)
Securities, continuous unrealized loss position, fair value	53,767,360	70,434,596
Securities, continuous unrealized loss position, unrealized losses	(784,771)	(1,947,969)
US States and Political Subdivisions Debt Securities [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value		6,324,750
Securities, continuous unrealized loss position, less than 12 months, unrealized losses		(67,774)
Securities, continuous unrealized loss position, 12 months or more, fair value	13,015,347	23,223,221
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(135,409)	(642,935)
Securities, continuous unrealized loss position, fair value	13,015,347	29,547,971
Securities, continuous unrealized loss position, unrealized losses	(135,409)	(710,709)
Corporate Debt Securities [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	4,023,171
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(37,024)
Securities, continuous unrealized loss position, 12 months or more, fair value
Securities, continuous unrealized loss position, 12 months or more, unrealized losses
Securities, continuous unrealized loss position, fair value	4,023,171
Securities, continuous unrealized loss position, unrealized losses	(37,024)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	4,290,134	7,127,597
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(24,978)	(112,282)
Securities, continuous unrealized loss position, 12 months or more, fair value	32,438,708	33,759,028
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(587,360)	(1,124,978)
Securities, continuous unrealized loss position, fair value	36,728,842	40,886,625
Securities, continuous unrealized loss position, unrealized losses	$ (612,338)	$ (1,237,260)