Note 5 - Loans - Allowance for Loan Losses by Portfolio Segment and Based on Impairment Evaluation Method (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loans																$ 2,409,570	$ 2,305,375	$ 2,033,007
Loans individually evaluated for impairment																7,380	6,269	8,753
Loans collectively evaluated for impairment																2,401,714	2,298,482	2,023,432
Allowance for loan losses
Balance				$ 24,007				$ 22,441				$ 24,920	$ 24,007	$ 22,441	$ 24,920
Provision for loan losses	$ 900	$ 150	$ 600	900	$ 500	$ 1,250	$ 750	500	$ 750				2,550	3,000	750
Charge-offs													(2,429)	(2,493)	(5,381)
Recoveries													757	1,059	2,152
Balance	24,885				24,007				22,441				24,885	24,007	22,441
Allowance for loans individually evaluated for impairment																48	1,267	544
Allowance for loans collectively evaluated for impairment																24,837	22,740	21,897
Allowance for loans acquired with deteriorated credit quality	24,885			24,007	24,007			22,441	22,441			24,920	24,885	24,007	22,441	24,885	24,007	22,441
Loans																2,409,570	2,305,375	2,033,007
Loans individually evaluated for impairment																7,380	6,269	8,753
Loans collectively evaluated for impairment																2,401,714	2,298,482	2,023,432
Receivables Acquired with Deteriorated Credit Quality [Member]
Loans																476	624	822
Allowance for loan losses
Balance
Balance
Allowance for loans acquired with deteriorated credit quality
Loans																476	624	822
Commercial and Industrial Portfolio Segment [Member]
Loans																779,014	736,841	644,398
Loans individually evaluated for impairment																1,176	2,682	4,635
Loans collectively evaluated for impairment																777,838	734,139	639,760
Allowance for loan losses
Balance				10,483				8,645				11,819	10,483	8,645	11,819
Provision for loan losses													2,373	2,775	793
Charge-offs													(1,782)	(1,216)	(4,065)
Recoveries													202	279	98
Balance	11,276				10,483				8,645				11,276	10,483	8,645
Allowance for loans individually evaluated for impairment																34	1,207	268
Allowance for loans collectively evaluated for impairment																11,242	9,276	8,377
Allowance for loans acquired with deteriorated credit quality	11,276			10,483	10,483			8,645	8,645			11,819	10,483	10,483	8,645	11,276	10,483	8,645
Loans																779,014	736,841	644,398
Loans individually evaluated for impairment																1,176	2,682	4,635
Loans collectively evaluated for impairment																777,838	734,139	639,760
Commercial and Industrial Portfolio Segment [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Loans																	20	3
Allowance for loan losses
Balance
Balance
Allowance for loans acquired with deteriorated credit quality
Loans																	20	3
Construction and Development Excluding Undeveloped Land Portfolio Segment [Member]
Loans																195,912	192,348	134,482
Loans individually evaluated for impairment																664	538
Loans collectively evaluated for impairment																195,248	191,810	134,160
Allowance for loan losses
Balance				1,923				1,760				721	1,923	1,760	721
Provision for loan losses													(199)	275	1,065
Charge-offs														(133)	(26)
Recoveries														21
Balance	1,724				1,923				1,760				1,724	1,923	1,760
Allowance for loans individually evaluated for impairment
Allowance for loans collectively evaluated for impairment																1,724	1,923	1,760
Allowance for loans acquired with deteriorated credit quality	1,724			1,923	1,923			1,760	1,760			721	1,923	1,923	1,760	1,724	1,923	1,760
Loans																195,912	192,348	134,482
Loans individually evaluated for impairment																664	538
Loans collectively evaluated for impairment																195,248	191,810	134,160
Construction and Development Excluding Undeveloped Land Portfolio Segment [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Loans																		322
Allowance for loan losses
Balance
Balance
Allowance for loans acquired with deteriorated credit quality
Loans																		322
Undevelopment Land Portfolio Segment [Member]
Loans																18,988	21,496	21,185
Loans individually evaluated for impairment																474	474
Loans collectively evaluated for impairment																18,514	21,022	21,185
Allowance for loan losses
Balance				684				814				1,545	684	814	1,545
Provision for loan losses													(163)	(130)	(2,131)
Charge-offs
Recoveries															1,400
Balance	521				684				814				521	684	814
Allowance for loans individually evaluated for impairment																	1
Allowance for loans collectively evaluated for impairment																521	683	814
Allowance for loans acquired with deteriorated credit quality	521			684	684			814	814			1,545	684	684	814	521	684	814
Loans																18,988	21,496	21,185
Loans individually evaluated for impairment																474	474
Loans collectively evaluated for impairment																18,514	21,022	21,185
Undevelopment Land Portfolio Segment [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Loans
Allowance for loan losses
Balance
Balance
Allowance for loans acquired with deteriorated credit quality
Loans
Real Estate Mortgage Portfolio Segment [Member]
Loans																1,376,788	1,319,520	1,197,411
Loans individually evaluated for impairment																5,066	2,516	4,050
Loans collectively evaluated for impairment																1,371,246	1,316,400	1,192,864
Allowance for loan losses
Balance				10,573				10,875				10,541	10,573	10,875	10,541
Provision for loan losses													383	(68)	872
Charge-offs													(98)	(576)	(693)
Recoveries													154	342	155
Balance	11,012				10,573				10,875				11,012	10,573	10,875
Allowance for loans individually evaluated for impairment																14		208
Allowance for loans collectively evaluated for impairment																10,998	10,573	10,667
Allowance for loans acquired with deteriorated credit quality	11,012			10,573	10,573			10,875	10,875			10,541	10,573	10,573	10,875	11,012	10,573	10,875
Loans																1,376,788	1,319,520	1,197,411
Loans individually evaluated for impairment																5,066	2,516	4,050
Loans collectively evaluated for impairment																1,371,246	1,316,400	1,192,864
Real Estate Mortgage Portfolio Segment [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Loans																476	604	497
Allowance for loan losses
Balance
Balance
Allowance for loans acquired with deteriorated credit quality
Loans																476	604	497
Consumer Portfolio Segment [Member]
Loans																38,868	35,170	35,531
Loans individually evaluated for impairment																	59	68
Loans collectively evaluated for impairment																38,868	35,111	35,463
Allowance for loan losses
Balance				344				347				294	344	347	294
Provision for loan losses													156	148	151
Charge-offs													(549)	(568)	(597)
Recoveries													401	417	499
Balance	352				344				347				352	344	347
Allowance for loans individually evaluated for impairment																	59	68
Allowance for loans collectively evaluated for impairment																352	285	279
Allowance for loans acquired with deteriorated credit quality	352			344	344			347	347			$ 294	344	344	347	352	344	347
Loans																38,868	35,170	35,531
Loans individually evaluated for impairment																	59	68
Loans collectively evaluated for impairment																38,868	35,111	35,463
Consumer Portfolio Segment [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Loans
Allowance for loan losses
Balance
Balance
Allowance for loans acquired with deteriorated credit quality
Loans