Note 5 - Loans - Aging of the Recorded Investment in Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current	$ 2,397,731	$ 2,295,871
Past due	11,839	9,504
Loans	2,409,570	2,305,375	$ 2,033,007
Recorded investment greater than 90 days and accruing	2	438
Financing Receivables, 30 to 59 Days Past Due [Member]
Past due	4,151	2,589
Financing Receivables, 60 to 89 Days Past Due [Member]
Past due	1,175	1,182
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	6,513	5,733
Commercial and Industrial Portfolio Segment [Member]
Current	776,118	734,682
Past due	2,896	2,159
Loans	779,014	736,841	644,398
Recorded investment greater than 90 days and accruing		18
Commercial and Industrial Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due	2,571	84
Commercial and Industrial Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due	4	290
Commercial and Industrial Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	321	1,785
Construction and Development Excluding Undeveloped Land Portfolio Segment [Member]
Current	194,936	191,810
Past due	976	538
Loans	195,912	192,348	134,482
Recorded investment greater than 90 days and accruing
Construction and Development Excluding Undeveloped Land Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due
Construction and Development Excluding Undeveloped Land Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due	312
Construction and Development Excluding Undeveloped Land Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	664	538
Undevelopment Land Portfolio Segment [Member]
Current	18,514	21,022
Past due	474	474
Loans	18,988	21,496	21,185
Recorded investment greater than 90 days and accruing
Undevelopment Land Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due
Undevelopment Land Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due
Undevelopment Land Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	474	474
Real Estate Mortgage Portfolio Segment [Member]
Current	1,369,464	1,313,392
Past due	7,324	6,128
Loans	1,376,788	1,319,520	1,197,411
Recorded investment greater than 90 days and accruing	2	420
Real Estate Mortgage Portfolio Segment [Member] | Commercial Investment [Member]
Current	594,242	537,998
Past due	660	888
Loans	594,902	538,886
Recorded investment greater than 90 days and accruing		86
Real Estate Mortgage Portfolio Segment [Member] | Owner Occupied Commercial [Member]
Current	394,623	406,726
Past due	4,062	1,566
Loans	398,685	408,292
Recorded investment greater than 90 days and accruing		182
Real Estate Mortgage Portfolio Segment [Member] | One to Four Family Residential [Member]
Current	259,994	246,730
Past due	2,116	2,768
Loans	262,110	249,498
Recorded investment greater than 90 days and accruing		34
Real Estate Mortgage Portfolio Segment [Member] | Home Equity First Lien [Member]
Current	56,938	55,027
Past due	172	298
Loans	57,110	55,325
Recorded investment greater than 90 days and accruing		46
Real Estate Mortgage Portfolio Segment [Member] | Home Equity Junior Lien [Member]
Current	63,667	66,911
Past due	314	608
Loans	63,981	67,519
Recorded investment greater than 90 days and accruing	2	72
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due	1,494	2,477
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Investment [Member]
Past due	608	631
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member] | Owner Occupied Commercial [Member]
Past due	455	342
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member] | One to Four Family Residential [Member]
Past due	172	1,174
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member] | Home Equity First Lien [Member]
Past due	172	231
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member] | Home Equity Junior Lien [Member]
Past due	87	99
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due	776	787
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Investment [Member]
Past due		64
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member] | Owner Occupied Commercial [Member]
Past due	275
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member] | One to Four Family Residential [Member]
Past due	307	576
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member] | Home Equity First Lien [Member]
Past due		21
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member] | Home Equity Junior Lien [Member]
Past due	194	126
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due	5,054	2,864
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Investment [Member]
Past due	52	193
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Owner Occupied Commercial [Member]
Past due	3,332	1,224
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | One to Four Family Residential [Member]
Past due	1,637	1,018
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Home Equity First Lien [Member]
Past due		46
Real Estate Mortgage Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Home Equity Junior Lien [Member]
Past due	33	383
Consumer Portfolio Segment [Member]
Current	38,699	34,965
Past due	169	205
Loans	38,868	35,170	$ 35,531
Recorded investment greater than 90 days and accruing
Consumer Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Past due	86	28
Consumer Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Past due	83	105
Consumer Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past due		$ 72