Note 4 - Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Securities, continuous unrealized loss position, less than 12 months, fair value	$ 44,830,810	$ 31,113,287
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(1,140,824)	(357,654)
Securities, continuous unrealized loss position, 12 months or more, fair value	28,065,468	30,994,373
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(1,314,434)	(814,880)
Securities, continuous unrealized loss position, fair value	72,896,278	62,107,660
Securities, continuous unrealized loss position, unrealized losses	(2,455,258)	(1,172,534)
US Government Agencies Debt Securities [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	1,015,035
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(176)
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	1,015,035
Securities, continuous unrealized loss position, unrealized losses	(176)
Corporate Debt Securities [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	999,834
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(166)
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	999,834
Securities, continuous unrealized loss position, unrealized losses	(166)
US States and Political Subdivisions Debt Securities [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	21,278,029	11,024,593
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(515,479)	(103,747)
Securities, continuous unrealized loss position, 12 months or more, fair value	8,539,798	8,802,796
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(367,917)	(159,874)
Securities, continuous unrealized loss position, fair value	29,817,827	19,827,389
Securities, continuous unrealized loss position, unrealized losses	(883,396)	(263,621)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities, continuous unrealized loss position, less than 12 months, fair value	21,537,912	20,088,694
Securities, continuous unrealized loss position, less than 12 months, unrealized losses	(625,003)	(253,907)
Securities, continuous unrealized loss position, 12 months or more, fair value	19,525,670	22,191,577
Securities, continuous unrealized loss position, 12 months or more, unrealized losses	(946,517)	(655,006)
Securities, continuous unrealized loss position, fair value	41,063,582	42,280,271
Securities, continuous unrealized loss position, unrealized losses	$ (1,571,520)	$ (908,913)