Note 6 - Loans and the Allowance for Loan Losses - Past Due Loans Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Past due	$ 10,029	$ 11,242
Current	1,287,930	964,042
Loans	1,297,959	975,284
Recorded investment over 90 days past due and still accruing	256	132
Financing Receivables, 30 to 59 Days Past Due [Member]
Past due	2,170	2,820
Financing Receivables, 60 to 89 Days Past Due [Member]
Past due	744	422
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	7,115	8,000
Commercial Real Estate Portfolio Segment [Member] | Construction and Land [Member]
Past due	91	91
Current	196,313	143,444
Loans	196,404	143,535
Recorded investment over 90 days past due and still accruing	27	0
Commercial Real Estate Portfolio Segment [Member] | Construction and Land [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due	42	0
Commercial Real Estate Portfolio Segment [Member] | Construction and Land [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due	20	0
Commercial Real Estate Portfolio Segment [Member] | Construction and Land [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	29	91
Commercial Real Estate Portfolio Segment [Member] | Farmland [Member]
Past due	0	0
Current	26,882	10,480
Loans	26,882	10,480
Recorded investment over 90 days past due and still accruing	0	0
Commercial Real Estate Portfolio Segment [Member] | Farmland [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due	0	0
Commercial Real Estate Portfolio Segment [Member] | Farmland [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due	0	0
Commercial Real Estate Portfolio Segment [Member] | Farmland [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	0	0
Commercial Real Estate Portfolio Segment [Member] | Nonfarm Nonresidential [Member]
Past due	3,765	5,776
Current	428,541	331,923
Loans	432,306	337,699
Recorded investment over 90 days past due and still accruing	0	0
Commercial Real Estate Portfolio Segment [Member] | Nonfarm Nonresidential [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due	251	2,344
Commercial Real Estate Portfolio Segment [Member] | Nonfarm Nonresidential [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due		103
Commercial Real Estate Portfolio Segment [Member] | Nonfarm Nonresidential [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	3,514	3,329
Residential Portfolio Segment [Member] | Real Estate Residential One- to Four-Family [Member]
Past due	2,782	1,728
Current	231,908	155,777
Loans	234,690	157,505
Recorded investment over 90 days past due and still accruing	122	73
Residential Portfolio Segment [Member] | Real Estate Residential One- to Four-Family [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due	1,251	470
Residential Portfolio Segment [Member] | Real Estate Residential One- to Four-Family [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due	356	319
Residential Portfolio Segment [Member] | Real Estate Residential One- to Four-Family [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	1,175	939
Residential Portfolio Segment [Member] | Multi-family Residential [Member]
Past due		0
Current	22,109	20,717
Loans	22,109	20,717
Recorded investment over 90 days past due and still accruing	0	0
Residential Portfolio Segment [Member] | Multi-family Residential [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due	0	0
Residential Portfolio Segment [Member] | Multi-family Residential [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due		0
Residential Portfolio Segment [Member] | Multi-family Residential [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	0	0
Commercial Portfolio Segment [Member]
Past due	3,094	3,274
Current	314,795	251,153
Loans	317,889	254,427
Recorded investment over 90 days past due and still accruing	78	59
Commercial Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due	507	0
Commercial Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due	297	0
Commercial Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	2,290	3,274
Consumer Portfolio Segment [Member]
Past due	297	373
Current	67,382	50,548
Loans	67,679	50,921
Recorded investment over 90 days past due and still accruing	29	0
Consumer Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due	119	6
Consumer Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due	71	0
Consumer Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	$ 107	$ 367