Note 4 - Loans - Allowance for Loan Losses (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Beginning balance	$ 2,509,334	$ 2,458,911	$ 2,458,911
Provision for loan losses	13,000	50,000	475,000
Charge offs		(10,622)	(702,115)
Recoveries	6,875	3,666	277,538
Ending balance	2,529,209	2,501,955	2,509,334
Allowance for loan losses, individually		28,577
Allowance for loan losses, collectively	2,529,209	2,473,378	2,509,334
Outstanding loan, individually	3,163,793	4,396,741	3,177,381
Outstanding loan, collectively	335,026,988	335,819,071	340,763,461
Commercial Real Estate Portfolio Segment [Member]
Beginning balance	1,754,372	1,867,397	1,867,397
Provision for loan losses	3,524	62,323	372,315
Charge offs			(690,000)
Recoveries	1,000	2,000	204,660
Ending balance	1,758,896	1,931,720	1,754,372
Allowance for loan losses, individually		28,577
Allowance for loan losses, collectively	1,758,896	1,903,143	1,754,372
Outstanding loan, individually	3,163,793	4,396,741	3,177,381
Outstanding loan, collectively	233,630,509	232,971,398	235,656,768
Construction and Land Development [Member]
Beginning balance	196,374	223,274	223,274
Provision for loan losses	(29,317)	16,225	(78,496)
Charge offs		(10,622)	(12,115)
Recoveries	3,375		63,711
Ending balance	170,432	228,877	196,374
Allowance for loan losses, individually
Allowance for loan losses, collectively	170,432	228,877	196,374
Outstanding loan, individually
Outstanding loan, collectively	15,914,131	19,247,095	18,265,505
Residential Portfolio Segment [Member]
Beginning balance	401,626	247,953	247,953
Provision for loan losses	32,059	(722)	153,673
Charge offs
Recoveries
Ending balance	433,685	247,231	401,626
Allowance for loan losses, individually
Allowance for loan losses, collectively	433,685	247,231	401,626
Outstanding loan, individually
Outstanding loan, collectively	63,019,749	59,083,653	63,024,106
Commercial Portfolio Segment [Member]
Beginning balance	102,610	87,353	87,353
Provision for loan losses	(3,482)	(2,648)	6,090
Charge offs
Recoveries	2,500	1,666	9,167
Ending balance	101,628	86,371	102,610
Allowance for loan losses, individually
Allowance for loan losses, collectively	101,628	86,371	102,610
Outstanding loan, individually
Outstanding loan, collectively	22,095,306	23,996,157	23,323,073
Consumer Portfolio Segment [Member]
Beginning balance	10,428	7,027	7,027
Provision for loan losses	(5,569)	729	3,401
Charge offs
Recoveries
Ending balance	4,859	7,756	10,428
Allowance for loan losses, individually
Allowance for loan losses, collectively	4,859	7,756	10,428
Outstanding loan, individually
Outstanding loan, collectively	367,293	520,768	494,009
Unallocated Financing Receivables [Member]
Beginning balance	43,924	25,907	25,907
Provision for loan losses	15,785	(25,907)	18,017
Charge offs
Recoveries
Ending balance	59,709		43,924
Allowance for loan losses, individually
Allowance for loan losses, collectively	59,709		43,924
Outstanding loan, individually
Outstanding loan, collectively