Note 6 - Loans and the Allowance for Loan Losses - Past Due Loans Receivable (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Past due	$ 11,242,000	$ 6,071,000
Current	964,042,000	804,880,000
Loans	975,284,000	810,951,000
Recorded investment over 90 days past due and still accruing	132,000	168,000
Financing Receivables, 30 to 59 Days Past Due [Member]
Past due	2,820,000	2,935,000
Financing Receivables, 60 to 89 Days Past Due [Member]
Past due	422,000	1,124,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	8,000,000	2,012,000
Commercial Real Estate Portfolio Segment [Member] | Construction and Land [Member]
Past due	91,000	571,000
Current	143,444,000	93,855,000
Loans	143,535,000	94,426,000
Recorded investment over 90 days past due and still accruing	0	0
Commercial Real Estate Portfolio Segment [Member] | Construction and Land [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due		465,000
Commercial Real Estate Portfolio Segment [Member] | Construction and Land [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due		0
Commercial Real Estate Portfolio Segment [Member] | Construction and Land [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	91,000	106,000
Commercial Real Estate Portfolio Segment [Member] | Farmland [Member]
Past due	0	0
Current	10,480,000	9,217,000
Loans	10,480,000	9,217,000
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	5,776,000	2,075,000
Current	331,923,000	295,982,000
Loans	337,699,000	298,057,000
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	2,344,000	1,370,000
Commercial Real Estate Portfolio Segment [Member] | Nonfarm Nonresidential [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due	103,000	173,000
Commercial Real Estate Portfolio Segment [Member] | Nonfarm Nonresidential [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	3,329,000	532,000
Residential Portfolio Segment [Member] | Real Estate Residential One- to Four-Family [Member]
Past due	1,728,000	2,531,000
Current	155,777,000	126,521,000
Loans	157,505,000	129,052,000
Recorded investment over 90 days past due and still accruing	73,000	117,000
Residential Portfolio Segment [Member] | Real Estate Residential One- to Four-Family [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due	470,000	989,000
Residential Portfolio Segment [Member] | Real Estate Residential One- to Four-Family [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due	319,000	579,000
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	939,000	963,000
Residential Portfolio Segment [Member] | Multi-family Residential [Member]
Past due	0	0
Current	20,717,000	22,737,000
Loans	20,717,000	22,737,000
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	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	3,274,000	679,000
Current	251,153,000	212,441,000
Loans	254,427,000	213,120,000
Recorded investment over 90 days past due and still accruing	59,000	51,000
Commercial Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due		45,000
Commercial Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due		372,000
Commercial Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	3,274,000	262,000
Consumer Portfolio Segment [Member]
Past due	373,000	215,000
Current	50,548,000	44,127,000
Loans	50,921,000	44,342,000
Recorded investment over 90 days past due and still accruing	0	0
Consumer Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due	6,000	66,000
Consumer Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due		0
Consumer Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	$ 367,000	$ 149,000