Note 3 - Loans and Allowance for Loan Losses - Nonperforming Loans (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Loans past due 90 days or more still accruing interest	$ 0	$ 0
Commercial Portfolio Segment [Member]
Loans past due 90 days or more still accruing interest	0	0
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
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]
Loans past due 90 days or more still accruing interest	0	0
Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member]
Loans past due 90 days or more still accruing interest	0	0
Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member]
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]
Loans past due 90 days or more still accruing interest	0	0
Retail Portfolio Segment [Member]
Loans past due 90 days or more still accruing interest	0	0
Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans past due 90 days or more still accruing interest	0	0
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans past due 90 days or more still accruing interest	0	0
Nonperforming Financial Instruments [Member]
Loans past due 90 days or more still accruing interest	0	0
Nonaccrual loans	4,141,000	2,284,000
Total nonperforming loans	4,141,000	2,284,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member]
Total nonperforming loans	1,682,000	136,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Total nonperforming loans	213,000	0
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Vacant Land and Land Development and Residential Construction Loan [Member]
Total nonperforming loans	198,000	0
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member]
Total nonperforming loans	1,248,000	134,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member]
Total nonperforming loans	23,000	0
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Real Estate Multi Family and Residential Rental Loan [Member]
Total nonperforming loans	0	2,000
Nonperforming Financial Instruments [Member] | Retail Portfolio Segment [Member]
Total nonperforming loans	2,459,000	2,148,000
Nonperforming Financial Instruments [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Total nonperforming loans	265,000	255,000
Nonperforming Financial Instruments [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Total nonperforming loans	$ 2,194,000	$ 1,893,000