Note 3 - Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Securities, continuous unrealized loss position, less than 12 months, fair value	$ 39,551,825	$ 13,452,347
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(307,898)	(180,056)
Securities, continuous unrealized loss position, 12 months or more, fair value	3,018,538	56,982,249
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(67,548)	(1,767,913)
Securities, continuous unrealized loss position, fair value	42,570,363	70,434,596
Securities, continuous unrealized loss position, unrealized losses	(375,446)	(1,947,969)
US Government Agencies Debt Securities [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	2,487,795
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(11,962)
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	2,487,795
Securities, continuous unrealized loss position, unrealized losses	(11,962)
US States and Political Subdivisions Debt Securities [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	7,083,208	6,324,750
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(125,693)	(67,774)
Securities, continuous unrealized loss position, 12 months or more, fair value		23,223,221
Securities, continuous unrealized loss position, 12 months or more, unrealized losses		(642,935)
Securities, continuous unrealized loss position, fair value	7,083,208	29,547,971
Securities, continuous unrealized loss position, unrealized losses	(125,693)	(710,709)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	18,112,148	7,127,597
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(125,906)	(112,282)
Securities, continuous unrealized loss position, 12 months or more, fair value	3,018,538	33,759,028
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(67,548)	(1,124,978)
Securities, continuous unrealized loss position, fair value	21,130,686	40,886,625
Securities, continuous unrealized loss position, unrealized losses	(193,454)	$ (1,237,260)
Corporate Debt Securities [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	2,452,005
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(14,945)
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	2,452,005
Securities, continuous unrealized loss position, unrealized losses	(14,945)
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	9,416,669
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(29,392)
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	9,416,669
Securities, continuous unrealized loss position, unrealized losses	$ (29,392)