Note 3 - Loans - Loans Individually Evaluated for Impairment by Class of Loans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Unpaid principal balance, with no related allowance recorded	$ 4,235	$ 3,867
Recorded investment, with no related allowance recorded	1,926	1,717
Average recorded investment, with no related allowance recorded	1,822	1,996
Interest income recognized, with no related allowance recorded	22	30
Cash basis interest income recognized, with no related allowance recorded	14	30
Unpaid principal balance, with an allowance recorded	218	489
Recorded investment, with an allowance recorded	218	453
Allowance for loan losses allocated, with an allowance recorded	20	42
Average recorded investment, with an allowance recorded	335	877
Interest income recognized, with an allowance recorded	4	11
Cash basis interest income recognized, with an allowance recorded
Unpaid principal balance, total	4,453	4,356
Recorded investment, total	2,144	2,170
Average recorded investment, total	2,157	2,873
Interest income recognized, total	26	41
Cash basis interest income recognized	14	30
Commercial Portfolio Segment [Member]
Unpaid principal balance, with no related allowance recorded	265	138
Recorded investment, with no related allowance recorded	158	50
Average recorded investment, with no related allowance recorded	104	52
Interest income recognized, with no related allowance recorded
Cash basis interest income recognized, with no related allowance recorded
Unpaid principal balance, with an allowance recorded		24
Recorded investment, with an allowance recorded		24
Allowance for loan losses allocated, with an allowance recorded		3
Average recorded investment, with an allowance recorded	12
Interest income recognized, with an allowance recorded
Cash basis interest income recognized, with an allowance recorded
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Unpaid principal balance, with no related allowance recorded
Recorded investment, with no related allowance recorded
Average recorded investment, with no related allowance recorded
Interest income recognized, with no related allowance recorded
Cash basis interest income recognized, with no related allowance recorded
Unpaid principal balance, with an allowance recorded	0	0
Recorded investment, with an allowance recorded	0	0
Allowance for loan losses allocated, with an allowance recorded	0	0
Average recorded investment, with an allowance recorded	0	0
Interest income recognized, with an allowance recorded	0	0
Cash basis interest income recognized, with an allowance recorded	0	0
Commercial Real Estate Portfolio Segment [Member] | Farmland Loans [Member]
Unpaid principal balance, with no related allowance recorded	414	380
Recorded investment, with no related allowance recorded	299	293
Average recorded investment, with no related allowance recorded	296	98
Interest income recognized, with no related allowance recorded	10	5
Cash basis interest income recognized, with no related allowance recorded	10	5
Unpaid principal balance, with an allowance recorded	143	282
Recorded investment, with an allowance recorded	143	282
Allowance for loan losses allocated, with an allowance recorded	19	37
Average recorded investment, with an allowance recorded	212	158
Interest income recognized, with an allowance recorded	2	0
Cash basis interest income recognized, with an allowance recorded
Commercial Real Estate Portfolio Segment [Member] | Nonfarm Nonresidential [Member]
Unpaid principal balance, with no related allowance recorded	1,043	1,057
Recorded investment, with no related allowance recorded	480	489
Average recorded investment, with no related allowance recorded	485	256
Interest income recognized, with no related allowance recorded	8	3
Cash basis interest income recognized, with no related allowance recorded		3
Unpaid principal balance, with an allowance recorded
Recorded investment, with an allowance recorded
Allowance for loan losses allocated, with an allowance recorded
Average recorded investment, with an allowance recorded
Interest income recognized, with an allowance recorded
Cash basis interest income recognized, with an allowance recorded
Residential Portfolio Segment [Member] | Multifamily Loans [Member]
Unpaid principal balance, with no related allowance recorded
Recorded investment, with no related allowance recorded
Average recorded investment, with no related allowance recorded
Interest income recognized, with no related allowance recorded
Cash basis interest income recognized, with no related allowance recorded
Unpaid principal balance, with an allowance recorded
Recorded investment, with an allowance recorded
Allowance for loan losses allocated, with an allowance recorded
Average recorded investment, with an allowance recorded
Interest income recognized, with an allowance recorded
Cash basis interest income recognized, with an allowance recorded
Residential Portfolio Segment [Member] | One- to Four-family Residential Properties [Member]
Unpaid principal balance, with no related allowance recorded	1,862	1,679
Recorded investment, with no related allowance recorded	846	745
Average recorded investment, with no related allowance recorded	795	1,544
Interest income recognized, with no related allowance recorded	3	22
Cash basis interest income recognized, with no related allowance recorded	3	22
Unpaid principal balance, with an allowance recorded	75	183
Recorded investment, with an allowance recorded	75	147
Allowance for loan losses allocated, with an allowance recorded	1	2
Average recorded investment, with an allowance recorded	111	719
Interest income recognized, with an allowance recorded	2	11
Cash basis interest income recognized, with an allowance recorded
Consumer Portfolio Segment [Member]
Unpaid principal balance, with no related allowance recorded	354	309
Recorded investment, with no related allowance recorded	143	98
Average recorded investment, with no related allowance recorded	121	14
Interest income recognized, with no related allowance recorded	1
Cash basis interest income recognized, with no related allowance recorded	1
Unpaid principal balance, with an allowance recorded	0	0
Recorded investment, with an allowance recorded	0	0
Allowance for loan losses allocated, with an allowance recorded	0	0
Average recorded investment, with an allowance recorded
Interest income recognized, with an allowance recorded	0	0
Cash basis interest income recognized, with an allowance recorded	0	0
Agriculture Portfolio Segment [Member]
Unpaid principal balance, with no related allowance recorded	297	304
Recorded investment, with no related allowance recorded		42
Average recorded investment, with no related allowance recorded	21	32
Interest income recognized, with no related allowance recorded
Cash basis interest income recognized, with no related allowance recorded
Unpaid principal balance, with an allowance recorded
Recorded investment, with an allowance recorded
Allowance for loan losses allocated, with an allowance recorded
Average recorded investment, with an allowance recorded
Interest income recognized, with an allowance recorded	0	0
Cash basis interest income recognized, with an allowance recorded
Other Portfolio Segment [Member]
Unpaid principal balance, with no related allowance recorded	0	0
Recorded investment, with no related allowance recorded	0	0
Average recorded investment, with no related allowance recorded
Interest income recognized, with no related allowance recorded
Cash basis interest income recognized, with no related allowance recorded
Unpaid principal balance, with an allowance recorded	0	0
Recorded investment, with an allowance recorded	0	0
Allowance for loan losses allocated, with an allowance recorded	0	0
Average recorded investment, with an allowance recorded	0	0
Interest income recognized, with an allowance recorded	0	0
Cash basis interest income recognized, with an allowance recorded	$ 0	$ 0