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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Balance					$ 25,534				$ 24,885				$ 24,007	$ 25,534	$ 24,885	$ 24,007
Provision for loan and lease losses		$ 0	$ 400	$ 0	600	$ 0	$ 735	$ 1,235	735	$ 900	$ 150	$ 600	900	1,000	2,705	2,550
Charge-offs														(684)	(3,012)	(2,429)
Recoveries														941	956	757
Balance		26,791				25,534				24,885				26,791	25,534	24,885
Loans individually evaluated for impairment																	$ 11,530	$ 2,653
Loans collectively evaluated for impairment																	2,833,486	2,545,518
Loans	[1]																2,845,016	2,548,171
Allowance for loans individually evaluated for impairment																	1,163	42
Allowance for loans collectively evaluated for impairment																	25,628	25,492
Allowance for loan losses		26,791			25,534	25,534			24,885	24,885			24,007	25,534	24,885	24,007	26,791	25,534
Financial Asset Acquired with Credit Deterioration [Member]
Balance					0									0
Balance		0				0								0	0
Loans																	0	0
Allowance for loan losses		0			0	0								0	0		0	0
Commercial and Industrial Portfolio Segment [Member]
Balance					11,965				11,276				10,483	11,965	11,276	10,483
Provision for loan and lease losses														684	2,539	2,373
Charge-offs														(94)	(2,404)	(1,782)
Recoveries														267	554	202
Balance		12,822				11,965				11,276				12,822	11,965	11,276
Loans individually evaluated for impairment																	8,223	220
Loans collectively evaluated for impairment																	862,288	833,304
Loans																	870,511	833,524
Allowance for loans individually evaluated for impairment																	1,150	28
Allowance for loans collectively evaluated for impairment																	11,672	11,937
Allowance for loan losses		12,822			11,965	11,965			11,276	11,276			10,483	12,822	11,276	10,483	12,822	11,965
Commercial and Industrial Portfolio Segment [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Balance					0									0
Balance		0				0								0	0
Loans																	0	0
Allowance for loan losses		0			0	0								0	0		0	0
Construction and Development Excluding Undeveloped Land Portfolio Segment [Member]
Balance					1,760				1,724				1,923	1,760	1,724	1,923
Provision for loan and lease losses														(644)	36	(199)
Charge-offs														0	0	0
Recoveries														203	0	0
Balance		1,319				1,760				1,724				1,319	1,760	1,724
Loans individually evaluated for impairment																	0	318
Loans collectively evaluated for impairment																	213,822	224,732
Loans	[2]																213,822	225,050
Allowance for loans individually evaluated for impairment																	0	0
Allowance for loans collectively evaluated for impairment																	1,319	1,760
Allowance for loan losses		1,319			1,760	1,760			1,724	1,724			1,923	1,319	1,724	1,923	1,319	1,760
Construction and Development Excluding Undeveloped Land Portfolio Segment [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Balance					0									0
Balance		0				0								0	0
Loans																	0	0
Allowance for loan losses		0			0	0								0	0		0	0
Undevelopment Land Portfolio Segment [Member]
Balance					752				521				684	752	521	684
Provision for loan and lease losses														34	231	(163)
Charge-offs														0	0	0
Recoveries														0	0	0
Balance		786				752				521				786	752	521
Loans individually evaluated for impairment																	0	474
Loans collectively evaluated for impairment																	46,360	29,618
Loans																	46,360	30,092
Allowance for loans individually evaluated for impairment																	0	0
Allowance for loans collectively evaluated for impairment																	786	752
Allowance for loan losses		786			752	752			521	521			684	786	521	684	786	752
Undevelopment Land Portfolio Segment [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Balance					0									0
Balance		0				0								0	0
Loans																	0	0
Allowance for loan losses		0			0	0								0	0		0	0
Real Estate Mortgage Portfolio Segment [Member]
Balance					10,681				11,012				10,573	10,681	11,012	10,573
Provision for loan and lease losses														1,021	(261)	383
Charge-offs														(38)	(132)	(98)
Recoveries														100	62	154
Balance		11,764				10,681				11,012				11,764	10,681	11,012
Loans individually evaluated for impairment																	3,307	1,641
Loans collectively evaluated for impairment																	1,663,549	1,409,806
Loans																	1,666,856	1,411,447
Allowance for loans individually evaluated for impairment																	13	14
Allowance for loans collectively evaluated for impairment																	11,751	10,667
Allowance for loan losses		11,764			10,681	10,681			11,012	11,012			10,573	11,764	11,012	10,573	11,764	10,681
Real Estate Mortgage Portfolio Segment [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Balance					0									0
Balance		0				0								0	0
Loans																	0	0
Allowance for loan losses		0			0	0								0	0		0	0
Consumer Portfolio Segment [Member]
Balance					376				352				344	376	352	344
Provision for loan and lease losses														(95)	160	156
Charge-offs														(552)	(476)	(549)
Recoveries														371	340	401
Balance		100				376				352				100	376	352
Loans individually evaluated for impairment																	0	0
Loans collectively evaluated for impairment																	47,467	48,058
Loans																	47,467	48,058
Allowance for loans individually evaluated for impairment																	0	0
Allowance for loans collectively evaluated for impairment																	100	376
Allowance for loan losses		100			376	376			$ 352	$ 352			$ 344	100	352	$ 344	100	376
Consumer Portfolio Segment [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Balance					0									0
Balance		0				0								0	0
Loans																	0	0
Allowance for loan losses		$ 0			$ 0	$ 0								$ 0	$ 0		$ 0	$ 0

[1] Total loans are presented inclusive of premiums, discounts, and net loan origination fees and costs.

[2] Consists of land acquired for development by the borrower, but for which no development has yet taken place.