Note 15 - Financial Instruments With Off-balance Sheet Risk - Contractual Amount of Financial Instruments with Off-balance Sheet Risk (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Standby Letters of Credit [Member]
Financial instruments with off-balance sheet risk	$ 2,900	$ 4,100
Commitments to Extend Credit [Member]
Financial instruments with off-balance sheet risk	220,000	188,000
Fixed Rate [Member]
Financial instruments with off-balance sheet risk	109,991	73,653
Fixed Rate [Member] | Standby Letters of Credit [Member]
Financial instruments with off-balance sheet risk	1,722	2,284
Fixed Rate [Member] | Commitments to Extend Credit [Member]
Financial instruments with off-balance sheet risk	108,269	71,369
Variable Rate [Member]
Financial instruments with off-balance sheet risk	112,757	118,695
Variable Rate [Member] | Standby Letters of Credit [Member]
Financial instruments with off-balance sheet risk	1,154	1,769
Variable Rate [Member] | Commitments to Extend Credit [Member]
Financial instruments with off-balance sheet risk	$ 111,603	$ 116,926