Note 6 - Loans and the Allowance for Loan Losses - Loan Receivables on Nonaccrual Status (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Loans receivable on nonaccrual status	$ 12,535	$ 7,126
Commercial Real Estate Portfolio Segment [Member] | Construction and Land [Member]
Loans receivable on nonaccrual status	92	243
Commercial Real Estate Portfolio Segment [Member] | Farmland [Member]
Loans receivable on nonaccrual status
Commercial Real Estate Portfolio Segment [Member] | Nonfarm Nonresidential [Member]
Loans receivable on nonaccrual status	5,935	1,201
Residential Portfolio Segment [Member] | Real Estate Residential One- to Four-Family [Member]
Loans receivable on nonaccrual status	2,429	2,721
Residential Portfolio Segment [Member] | Multi-family Residential [Member]
Loans receivable on nonaccrual status
Commercial Portfolio Segment [Member]
Loans receivable on nonaccrual status	3,638	2,763
Consumer Portfolio Segment [Member]
Loans receivable on nonaccrual status	$ 441	$ 198