Note 3 - Loans and Allowance for Loan Losses - Nonperforming Loans (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
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	2,793,000	3,384,000
Total nonperforming loans	2,793,000	3,384,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member]
Total nonperforming loans	452,000	813,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Total nonperforming loans	169,000	172,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Vacant Land and Land Development and Residential Construction Loan [Member]
Total nonperforming loans	0	0
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member]
Total nonperforming loans	283,000	619,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member]
Total nonperforming loans	0	22,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Real Estate Multi Family and Residential Rental Loan [Member]
Total nonperforming loans	0	0
Nonperforming Financial Instruments [Member] | Retail Portfolio Segment [Member]
Total nonperforming loans	2,341,000	2,571,000
Nonperforming Financial Instruments [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Total nonperforming loans	175,000	242,000
Nonperforming Financial Instruments [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Total nonperforming loans	$ 2,166,000	$ 2,329,000