Note 3 - Loans and Allowance for Loan Losses - Nonperforming Loans (Details) - USD ($)	Dec. 31, 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	3,384,000	2,284,000
Total nonperforming loans	3,384,000	2,284,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member]
Total nonperforming loans	813,000	136,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Total nonperforming loans	172,000	0
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	619,000	134,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member]
Total nonperforming loans	22,000	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	2,571,000	2,148,000
Nonperforming Financial Instruments [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Total nonperforming loans	242,000	255,000
Nonperforming Financial Instruments [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Total nonperforming loans	$ 2,329,000	$ 1,893,000