Note 8 - Loans - Average Balance and Interest Income Recognized Related to Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Impaired Loans Average Recorded Investment	$ 123,851	$ 127,259	$ 127,756	$ 127,722
Impaired Loans Interest Income Recognized	1,145	1,264	3,188	2,349
Commercial Portfolio Segment [Member]
Impaired Loans Average Recorded Investment	48,772	24,987	46,920	22,572
Impaired Loans Interest Income Recognized	461	678	1,152	760
Real Estate Construction Portfolio Segment [Member]
Impaired Loans Average Recorded Investment	5,980	29,780	7,490	29,868
Impaired Loans Interest Income Recognized		99		287
Commercial Real Estate Portfolio Segment [Member]
Impaired Loans Average Recorded Investment	55,375	58,555	59,314	60,074
Impaired Loans Interest Income Recognized	576	391	1,757	1,015
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Impaired Loans Average Recorded Investment	13,724	13,937	14,032	15,208
Impaired Loans Interest Income Recognized	$ 108	$ 96	$ 279	$ 287