Note 5 - Loans - Average Balance and Interest Income Recognized Related to Impaired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Average Recorded Investment	$ 127,067	$ 131,019	$ 162,945
Contractual interest due	3,302	3,462	3,997
Commercial Portfolio Segment [Member]
Average Recorded Investment	26,957	21,199	23,960
Contractual interest due	1,303	767	546
Real Estate Construction Portfolio Segment [Member]
Average Recorded Investment	26,695	10,362	22,066
Contractual interest due			261
Commercial Real Estate Portfolio Segment [Member]
Average Recorded Investment	58,635	81,905	100,118
Contractual interest due	1,618	2,214	2,708
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Average Recorded Investment	14,780	17,553	16,801
Contractual interest due	$ 381	$ 481	$ 482