Note 5 - Loans - Impaired Loans and Related Allowance for Credit Losses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Loans with no related allowance, unpaid principal balance	$ 91,430	$ 95,807
Loans with no related allowance, recorded investment	83,217	88,342
Loans with related allowance, unpaid principal balance	35,646	28,637
Loans with related allowance, recorded investment	34,136	26,732
Allowance	2,134	2,796
Total impaired loans, unpaid principal balance	127,076	124,444
Total impaired loans, recorded investment	117,353	115,074
Commercial Portfolio Segment [Member]
Loans with no related allowance, unpaid principal balance	43,483	24,037
Loans with no related allowance, recorded investment	42,702	23,121
Loans with related allowance, unpaid principal balance	891	5,216
Loans with related allowance, recorded investment	793	4,640
Allowance	43	1,827
Real Estate Construction Portfolio Segment [Member]
Loans with no related allowance, unpaid principal balance	8,821	5,776
Loans with no related allowance, recorded investment	8,185	5,458
Commercial Real Estate Portfolio Segment [Member]
Loans with no related allowance, unpaid principal balance	37,825	60,522
Loans with no related allowance, recorded investment	31,029	54,453
Loans with related allowance, unpaid principal balance	21,733	10,158
Loans with related allowance, recorded investment	21,635	10,017
Allowance	1,738	573
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans with no related allowance, unpaid principal balance	1,301	5,472
Loans with no related allowance, recorded investment	1,301	5,310
Loans with related allowance, unpaid principal balance	13,022	13,263
Loans with related allowance, recorded investment	11,708	12,075
Allowance	$ 353	$ 396