Note 16 - Quarterly Results of Operations - Summary of Quarterly Results (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Total income	$ 4,776,334	$ 4,719,012	$ 4,659,456	$ 4,547,536	$ 4,599,891	$ 4,525,190	$ 4,385,506	$ 4,257,746	$ 18,702,338	$ 17,768,333
Interest expense	977,295	956,411	924,864	821,383	726,549	664,018	580,913	535,761	3,679,953	2,507,241
Net interest income	3,799,039	3,762,601	3,734,592	3,726,153	3,873,342	3,861,172	3,804,593	3,721,985	15,022,385	15,261,092
Provision for loan losses	40,000	(13,000)	0	13,000	450,000	(100,000)	75,000	50,000	40,000	475,000
Net Income	$ 1,060,786	$ 1,177,910	$ 1,225,821	$ 1,096,287	$ 1,136,805	$ 1,308,688	$ 1,145,065	$ 1,122,118	$ 4,560,804	$ 4,712,676
Earnings per share - basic and diluted (in dollars per share)	$ 0.36	$ 0.40	$ 0.42	$ 0.37	$ 0.39	$ 0.45	$ 0.39	$ 0.38	$ 1.54	$ 1.61