Note 1 - Basis of Presentation and Summary of Significant Accounting Policies - Impact of Adoption of Accounting Policy (Details) - USD ($)		Sep. 30, 2020	Jun. 30, 2020	Jan. 01, 2020		Dec. 31, 2019		Sep. 30, 2019	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Allowance for loans		$ 50,501,000	$ 47,708,000	$ 36,647,000	[1]	$ 26,791,000	[1]	$ 26,877,000	$ 26,416,000		$ 25,534,000
Total allowance for credit losses on off-balance sheet exposures		6,000,000		3,850,000		350,000				$ 3,900,000
Accounting Standards Update 2016-13 [Member]
Allowance for loans	[1]			9,856,000
Total allowance for credit losses on off-balance sheet exposures				3,500,000
Home Equity Line of Credit [Member]
Allowance for loans		938,000	832,000	842,000		728,000
Home Equity Line of Credit [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for loans				114,000
Commercial Real Estate Portfolio Segment [Member]
Allowance for loans		25,169,000	25,545,000	14,552,000		8,562,000
Commercial Real Estate Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for loans				5,990,000
Commercial Real Estate Portfolio Segment [Member] | Non-owner Occupied [Member]
Allowance for loans		18,140,000	18,839,000	8,333,000		5,235,000
Commercial Real Estate Portfolio Segment [Member] | Non-owner Occupied [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for loans				3,098,000
Commercial Real Estate Portfolio Segment [Member] | Owner Occupied [Member]
Allowance for loans		7,029,000	6,706,000	6,219,000		3,327,000
Commercial Real Estate Portfolio Segment [Member] | Owner Occupied [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for loans				2,892,000
Commercial and Industrial Portfolio Segment [Member]
Allowance for loans						12,822,000		11,953,000	11,858,000		11,965,000
Commercial and Industrial Portfolio Segment [Member] | Term, Excluding PPP [Member]
Allowance for loans				7,147,000		6,782,000
Commercial and Industrial Portfolio Segment [Member] | Term, Excluding PPP [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for loans				365,000
Commercial and Industrial Portfolio Segment [Member] | Lines of Credit [Member]
Allowance for loans		3,421,000	3,242,000	4,129,000		5,657,000
Commercial and Industrial Portfolio Segment [Member] | Lines of Credit [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for loans				(1,528,000)
Total Commercial and Industrial Portfolio Segment [Member]
Allowance for loans		12,365,000	10,581,000	11,276,000		12,439,000
Total Commercial and Industrial Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for loans				(1,163,000)
Residential Real Estate Portfolio Segment [Member]
Allowance for loans		5,274,000	4,442,000	4,089,000		2,474,000
Residential Real Estate Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for loans				1,615,000
Residential Real Estate Portfolio Segment [Member] | Non-owner Occupied [Member]
Allowance for loans		2,010,000	1,594,000	1,376,000		947,000
Residential Real Estate Portfolio Segment [Member] | Non-owner Occupied [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for loans				429,000
Residential Real Estate Portfolio Segment [Member] | Owner Occupied [Member]
Allowance for loans		3,264,000	2,848,000	2,713,000		1,527,000
Residential Real Estate Portfolio Segment [Member] | Owner Occupied [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for loans				1,186,000
Construction and Development [Member]
Allowance for loans		6,028,000	5,608,000	5,161,000		2,105,000		1,702,000	1,810,000		1,760,000
Construction and Development [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for loans				3,056,000
Consumer Portfolio Segment [Member]
Allowance for loans		336,000	362,000	398,000		100,000		$ 81,000	$ 117,000		$ 376,000
Consumer Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for loans				298,000
Finance Leases Portfolio Segment [Member]
Allowance for loans		$ 257,000	$ 223,000	233,000		237,000
Finance Leases Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for loans				(4,000)
Commercial Portfolio Segment [Member]
Allowance for loans				96,000		$ 146,000
Commercial Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for loans				$ (50,000)

[1] The impact of the ASC 326 adoption on the ACL on loans reflects $8.2 million related to the transition from the incurred loss ACL model to the CECL ACL model and $1.6 million related to the transition from PCI to PCD methodology as defined in the standard.