Note 1 - Basis of Presentation and Summary of Significant Accounting Policies - Impact of Adoption of Accounting Policy (Details) - USD ($)		Mar. 31, 2020	Jan. 01, 2020		Dec. 31, 2019		Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Allowance for loans		$ 42,143,000	$ 36,647,000	[1]	$ 26,791,000	[1]	$ 26,464,000		$ 25,534,000
Total allowance for credit losses on off-balance sheet exposures			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		623,000	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		19,944,000	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		13,435,000	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		6,509,000	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		11,762,000		11,965,000
Commercial and Industrial Portfolio Segment [Member] | Term [Member]
Allowance for loans		7,990,000	7,147,000		6,782,000
Commercial and Industrial Portfolio Segment [Member] | Term [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		3,866,000	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		11,856,000	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		4,121,000	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		1,419,000	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		2,702,000	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		5,185,000	5,161,000		2,105,000		1,884,000		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		198,000	398,000		100,000		$ 155,000		$ 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		$ 159,000	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 for 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.