Note 3 - Loans - Loans Individually Evaluated for Impairment by Class of Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Unpaid principal balance, with no related allowance recorded	$ 3,867	$ 5,072	$ 9,739
Recorded investment, with no related allowance recorded	1,717	2,032	5,910
Average recorded investment, with no related allowance recorded	2,036	3,573	7,592
Interest income recognized, with no related allowance recorded	288	379	422
Cash basis interest income recognized, with no related allowance recorded	229	360	410
Unpaid principal balance, with an allowance recorded	489	879	1,263
Recorded investment, with an allowance recorded	453	879	1,263
Allowance for loan losses allocated, with an allowance recorded	42	203	219
Average recorded investment, with an allowance recorded	710	1,271	2,001
Interest income recognized, with an allowance recorded	17	3	89
Cash basis interest income recognized, with an allowance recorded
Unpaid principal balance, total	4,356	5,951	11,002
Recorded investment, total	2,170	2,911	7,173
Average recorded investment, total	2,746	4,844	9,593
Interest income recognized, total	305	382	511
Cash basis interest income recognized	229	360	410
Commercial Portfolio Segment [Member]
Unpaid principal balance, with no related allowance recorded	138	120	703
Recorded investment, with no related allowance recorded	50	53	487
Average recorded investment, with no related allowance recorded	57	125	495
Interest income recognized, with no related allowance recorded	3		7
Cash basis interest income recognized, with no related allowance recorded	3		7
Unpaid principal balance, with an allowance recorded	24		100
Recorded investment, with an allowance recorded	24		100
Allowance for loan losses allocated, with an allowance recorded	3		13
Average recorded investment, with an allowance recorded	15	60	100
Interest income recognized, with an allowance recorded	2	3	7
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	0
Recorded investment, with an allowance recorded	0	0	0
Allowance for loan losses allocated, with an allowance recorded	0	0	0
Average recorded investment, with an allowance recorded	0	0	0
Interest income recognized, with an allowance recorded	0	0	0
Cash basis interest income recognized, with an allowance recorded	0	0	0
Commercial Real Estate Portfolio Segment [Member] | Farmland Loans [Member]
Unpaid principal balance, with no related allowance recorded	380	1,860	3,687
Recorded investment, with no related allowance recorded	293	89	2,059
Average recorded investment, with no related allowance recorded	179	1,156	2,651
Interest income recognized, with no related allowance recorded	23	360	210
Cash basis interest income recognized, with no related allowance recorded	23	360	210
Unpaid principal balance, with an allowance recorded	282
Recorded investment, with an allowance recorded	282
Allowance for loan losses allocated, with an allowance recorded	37
Average recorded investment, with an allowance recorded	236		235
Interest income recognized, with an allowance recorded	9	0	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	1,057	402	1,047
Recorded investment, with no related allowance recorded	489	262	576
Average recorded investment, with no related allowance recorded	295	327	716
Interest income recognized, with no related allowance recorded	34	19	59
Cash basis interest income recognized, with no related allowance recorded	3		47
Unpaid principal balance, with an allowance recorded		159
Recorded investment, with an allowance recorded		159
Allowance for loan losses allocated, with an allowance recorded		35
Average recorded investment, with an allowance recorded		100	238
Interest income recognized, with an allowance recorded			14
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			820
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	1,679	2,678	4,293
Recorded investment, with no related allowance recorded	745	1,628	2,787
Average recorded investment, with no related allowance recorded	1,402	1,964	2,884
Interest income recognized, with no related allowance recorded	219		143
Cash basis interest income recognized, with no related allowance recorded	191		143
Unpaid principal balance, with an allowance recorded	183	720	1,163
Recorded investment, with an allowance recorded	147	720	1,163
Allowance for loan losses allocated, with an allowance recorded	2	168	206
Average recorded investment, with an allowance recorded	459	1,111	1,404
Interest income recognized, with an allowance recorded	6		68
Cash basis interest income recognized, with an allowance recorded
Consumer Portfolio Segment [Member]
Unpaid principal balance, with no related allowance recorded	309	12	9
Recorded investment, with no related allowance recorded	98		1
Average recorded investment, with no related allowance recorded	56	1	2
Interest income recognized, with no related allowance recorded	6		2
Cash basis interest income recognized, with no related allowance recorded	6		2
Unpaid principal balance, with an allowance recorded	0	0	0
Recorded investment, with an allowance recorded	0	0	0
Allowance for loan losses allocated, with an allowance recorded	0	0	0
Average recorded investment, with an allowance recorded
Interest income recognized, with an allowance recorded	0	0	0
Cash basis interest income recognized, with an allowance recorded	0	0	0
Agriculture Portfolio Segment [Member]
Unpaid principal balance, with no related allowance recorded	304
Recorded investment, with no related allowance recorded	42
Average recorded investment, with no related allowance recorded	47		24
Interest income recognized, with no related allowance recorded	3		1
Cash basis interest income recognized, with no related allowance recorded	3		1
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			24
Interest income recognized, with an allowance recorded	0	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	0
Recorded investment, with no related allowance recorded	0	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	0
Recorded investment, with an allowance recorded	0	0	0
Allowance for loan losses allocated, with an allowance recorded	0	0	0
Average recorded investment, with an allowance recorded	0	0	0
Interest income recognized, with an allowance recorded	0	0	0
Cash basis interest income recognized, with an allowance recorded	$ 0	$ 0	$ 0