Note 3 - Loans and Allowance for Loan Losses - Age Analysis of Past Due Loans (Details) - USD ($)		Sep. 30, 2020	Dec. 31, 2019
Past due loans		$ 2,127,000	$ 1,884,000
Current loans		3,348,417,000	2,854,783,000
Loans		3,350,544,000	2,856,667,000
Loans past due 90 days or more still accruing interest		0	0
Commercial Portfolio Segment [Member]
Past due loans		1,315,000	325,000
Current loans		2,937,046,000	2,441,219,000
Loans		2,938,361,000	2,441,544,000
Loans past due 90 days or more still accruing interest		0	0
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Past due loans		104,000	0
Current loans		1,321,315,000	846,551,000
Loans	[1]	1,321,419,000	846,551,000
Loans past due 90 days or more still accruing interest		0	0
Commercial Portfolio Segment [Member] | Vacant Land and Land Development and Residential Construction Loan [Member]
Past due loans		236,000	191,000
Current loans		50,705,000	55,928,000
Loans		50,941,000	56,119,000
Loans past due 90 days or more still accruing interest		0	0
Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member]
Past due loans		952,000	134,000
Current loans		548,412,000	578,869,000
Loans		549,364,000	579,003,000
Loans past due 90 days or more still accruing interest		0	0
Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member]
Past due loans		23,000	0
Current loans		878,874,000	835,346,000
Loans		878,897,000	835,346,000
Loans past due 90 days or more still accruing interest		0	0
Commercial Portfolio Segment [Member] | Real Estate Multi Family and Residential Rental Loan [Member]
Past due loans		0	0
Current loans		137,740,000	124,525,000
Loans		137,740,000	124,525,000
Loans past due 90 days or more still accruing interest		0	0
Retail Portfolio Segment [Member]
Past due loans		812,000	1,559,000
Current loans		411,371,000	413,564,000
Loans		412,183,000	415,123,000
Loans past due 90 days or more still accruing interest		0	0
Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Past due loans		105,000	256,000
Current loans		63,618,000	75,118,000
Loans		63,723,000	75,374,000
Loans past due 90 days or more still accruing interest		0	0
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Past due loans		707,000	1,303,000
Current loans		347,753,000	338,446,000
Loans		348,460,000	339,749,000
Loans past due 90 days or more still accruing interest		0	0
Financial Asset, 30 to 59 Days Past Due [Member]
Past due loans		650,000	1,107,000
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Past due loans		397,000	191,000
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Past due loans		39,000	0
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Vacant Land and Land Development and Residential Construction Loan [Member]
Past due loans		16,000	191,000
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member]
Past due loans		342,000	0
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member]
Past due loans		0	0
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Real Estate Multi Family and Residential Rental Loan [Member]
Past due loans		0	0
Financial Asset, 30 to 59 Days Past Due [Member] | Retail Portfolio Segment [Member]
Past due loans		253,000	916,000
Financial Asset, 30 to 59 Days Past Due [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Past due loans		50,000	171,000
Financial Asset, 30 to 59 Days Past Due [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Past due loans		203,000	745,000
Financial Asset, 60 to 89 Days Past Due [Member]
Past due loans		854,000	94,000
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Past due loans		598,000	0
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Past due loans		35,000	0
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Vacant Land and Land Development and Residential Construction Loan [Member]
Past due loans		22,000	0
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member]
Past due loans		518,000	0
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member]
Past due loans		23,000	0
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Real Estate Multi Family and Residential Rental Loan [Member]
Past due loans		0	0
Financial Asset, 60 to 89 Days Past Due [Member] | Retail Portfolio Segment [Member]
Past due loans		256,000	94,000
Financial Asset, 60 to 89 Days Past Due [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Past due loans		3,000	65,000
Financial Asset, 60 to 89 Days Past Due [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Past due loans		253,000	29,000
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Past due loans		623,000	683,000
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Past due loans		320,000	134,000
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Past due loans		30,000	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Vacant Land and Land Development and Residential Construction Loan [Member]
Past due loans		198,000	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member]
Past due loans		92,000	134,000
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member]
Past due loans		0	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Real Estate Multi Family and Residential Rental Loan [Member]
Past due loans		0	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Retail Portfolio Segment [Member]
Past due loans		303,000	549,000
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Past due loans		52,000	20,000
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Past due loans		$ 251,000	$ 529,000

[1] For September 30, 2020, includes $555 million in loans originated under the Paycheck Protection Program.