Note 3 - Loans and Allowance for Loan Losses - Loans Modified As Troubled Debt Restructurings Within the Previous Twelve Months That Became Over 30 Days Past Due (Details)	3 Months Ended	9 Months Ended
Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Originated Loan [Member]
Number of Contracts	0	0	0	0
Recorded Principal Balance	$ 0	$ 0	$ 0	$ 0
Originated Loan [Member] \| Commercial Portfolio Segment [Member]
Number of Contracts	0	0	0	0
Recorded Principal Balance	$ 0	$ 0	$ 0	$ 0
Originated Loan [Member] \| Commercial Portfolio Segment [Member] \| Commercial and Industrial [Member]
Number of Contracts	0	0	0	0
Recorded Principal Balance	$ 0	$ 0	$ 0	$ 0
Originated Loan [Member] \| Commercial Portfolio Segment [Member] \| Vacant Land and Land Development and Residential Construction Loan [Member]
Number of Contracts	0	0	0	0
Recorded Principal Balance	$ 0	$ 0	$ 0	$ 0
Originated Loan [Member] \| Commercial Portfolio Segment [Member] \| Real Estate Owner Occupied Loan [Member]
Number of Contracts	0	0	0	0
Recorded Principal Balance	$ 0	$ 0	$ 0	$ 0
Originated Loan [Member] \| Commercial Portfolio Segment [Member] \| Real Estate Non Owner Occupied Loan [Member]
Number of Contracts	0	0	0	0
Recorded Principal Balance	$ 0	$ 0	$ 0	$ 0
Originated Loan [Member] \| Commercial Portfolio Segment [Member] \| Real Estate Multi Family and Residential Rental Loan [Member]
Number of Contracts	0	0	0	0
Recorded Principal Balance	$ 0	$ 0	$ 0	$ 0
Originated Loan [Member] \| Retail Portfolio Segment [Member]
Number of Contracts	0	0	0	0
Recorded Principal Balance	$ 0	$ 0	$ 0	$ 0
Originated Loan [Member] \| Retail Portfolio Segment [Member] \| Home Equity and Other [Member]
Number of Contracts	0	0	0	0
Recorded Principal Balance	$ 0	$ 0	$ 0	$ 0
Originated Loan [Member] \| Retail Portfolio Segment [Member] \| One to Four Family Mortgages [Member]
Number of Contracts	0	0	0	0
Recorded Principal Balance	$ 0	$ 0	$ 0	$ 0
Acquired Loan [Member]
Number of Contracts	0	2	0	2
Recorded Principal Balance	$ 0	$ 213,000	$ 0	$ 213,000
Acquired Loan [Member] \| Commercial Portfolio Segment [Member]
Number of Contracts	0	1	0	1
Recorded Principal Balance	$ 0	$ 114,000	$ 0	$ 114,000
Acquired Loan [Member] \| Commercial Portfolio Segment [Member] \| Commercial and Industrial [Member]
Number of Contracts	0	1	0	1
Recorded Principal Balance	$ 0	$ 114,000	$ 0	$ 114,000
Acquired Loan [Member] \| Commercial Portfolio Segment [Member] \| Vacant Land and Land Development and Residential Construction Loan [Member]
Number of Contracts	0	0	0	0
Recorded Principal Balance	$ 0	$ 0	$ 0	$ 0
Acquired Loan [Member] \| Commercial Portfolio Segment [Member] \| Real Estate Owner Occupied Loan [Member]
Number of Contracts	0	0	0	0
Recorded Principal Balance	$ 0	$ 0	$ 0	$ 0
Acquired Loan [Member] \| Commercial Portfolio Segment [Member] \| Real Estate Non Owner Occupied Loan [Member]
Number of Contracts	0	0	0	0
Recorded Principal Balance	$ 0	$ 0	$ 0	$ 0
Acquired Loan [Member] \| Commercial Portfolio Segment [Member] \| Real Estate Multi Family and Residential Rental Loan [Member]
Number of Contracts	0	0	0	0
Recorded Principal Balance	$ 0	$ 0	$ 0	$ 0
Acquired Loan [Member] \| Retail Portfolio Segment [Member]
Number of Contracts	0	1	0	1
Recorded Principal Balance	$ 0	$ 99,000	$ 0	$ 99,000
Acquired Loan [Member] \| Retail Portfolio Segment [Member] \| Home Equity and Other [Member]
Number of Contracts	0	1	0	1
Recorded Principal Balance	$ 0	$ 99,000	$ 0	$ 99,000
Acquired Loan [Member] \| Retail Portfolio Segment [Member] \| One to Four Family Mortgages [Member]
Number of Contracts	0	0	0	0
Recorded Principal Balance	$ 0	$ 0	$ 0	$ 0

Note 3 - Loans and Allowance for Loan Losses - Loans Modified As Troubled Debt Restructurings Within the Previous Twelve Months That Became Over 30 Days Past Due (Details)