Note 4 - Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Securities, continuous unrealized loss position, less than 12 months, fair value	$ 16,197,612	$ 13,452,347
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(91,096)	(180,056)
Securities, continuous unrealized loss position, 12 months or more, fair value	4,429,589	56,982,249
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(96,895)	(1,767,913)
Securities, continuous unrealized loss position, fair value	20,627,201	70,434,596
Securities, continuous unrealized loss position, unrealized losses	(187,991)	(1,947,969)
US Government Agencies Debt Securities [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	1,490,680
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(9,071)
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	1,490,680
Securities, continuous unrealized loss position, unrealized losses	(9,071)
US States and Political Subdivisions Debt Securities [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	1,124,104	6,324,750
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(22,646)	(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	1,124,104	29,547,971
Securities, continuous unrealized loss position, unrealized losses	(22,646)	(710,709)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	8,979,065	7,127,597
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(46,080)	(112,282)
Securities, continuous unrealized loss position, 12 months or more, fair value	4,429,589	33,759,028
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(96,895)	(1,124,978)
Securities, continuous unrealized loss position, fair value	13,408,654	40,886,625
Securities, continuous unrealized loss position, unrealized losses	(142,975)	$ (1,237,260)
Corporate Debt Securities [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	2,540,521
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(13,115)
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	2,540,521
Securities, continuous unrealized loss position, unrealized losses	(13,115)
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	2,063,242
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(184)
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	2,063,242
Securities, continuous unrealized loss position, unrealized losses	$ (184)