Note 4 - Loans and Allowance for Loan Losses - Nonperforming Loans (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Originated Loan [Member]
Loans past due 90 days or more still accruing interest	$ 0	$ 0
Originated Loan [Member] | Commercial Portfolio Segment [Member]
Loans past due 90 days or more still accruing interest	0	0
Originated Loan [Member] | Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Loans past due 90 days or more still accruing interest	0	0
Originated Loan [Member] | 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
Originated Loan [Member] | Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member]
Loans past due 90 days or more still accruing interest	0	0
Originated Loan [Member] | Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member]
Loans past due 90 days or more still accruing interest	0	0
Originated Loan [Member] | 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
Originated Loan [Member] | Retail Portfolio Segment [Member]
Loans past due 90 days or more still accruing interest	0	0
Originated Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans past due 90 days or more still accruing interest	0	0
Originated Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans past due 90 days or more still accruing interest	0	0
Acquired Loan [Member]
Loans past due 90 days or more still accruing interest	0	0
Acquired Loan [Member] | Commercial Portfolio Segment [Member]
Loans past due 90 days or more still accruing interest	0	0
Acquired Loan [Member] | Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Loans past due 90 days or more still accruing interest	0	0
Acquired Loan [Member] | 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
Acquired Loan [Member] | Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member]
Loans past due 90 days or more still accruing interest	0	0
Acquired Loan [Member] | Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member]
Loans past due 90 days or more still accruing interest	0	0
Acquired Loan [Member] | 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
Acquired Loan [Member] | Retail Portfolio Segment [Member]
Loans past due 90 days or more still accruing interest	0	0
Acquired Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans past due 90 days or more still accruing interest	0	0
Acquired Loan [Member] | 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]
Total nonperforming loans	7,143,000	5,939,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member]
Total nonperforming loans	3,898,000	3,181,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Total nonperforming loans	1,444,000	2,296,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Vacant Land and Land Development and Residential Construction Loan [Member]
Total nonperforming loans	35,000	95,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member]
Total nonperforming loans	2,241,000	285,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member]
Total nonperforming loans	0	488,000
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Real Estate Multi Family and Residential Rental Loan [Member]
Total nonperforming loans	178,000	17,000
Nonperforming Financial Instruments [Member] | Retail Portfolio Segment [Member]
Total nonperforming loans	3,245,000	2,758,000
Nonperforming Financial Instruments [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Total nonperforming loans	577,000	496,000
Nonperforming Financial Instruments [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Total nonperforming loans	2,668,000	2,262,000
Nonperforming Financial Instruments [Member] | Originated Loan [Member]
Loans past due 90 days or more still accruing interest	0	0
Nonaccrual loans	3,672,000	3,328,000
Total nonperforming loans	3,672,000	3,328,000
Nonperforming Financial Instruments [Member] | Acquired Loan [Member]
Loans past due 90 days or more still accruing interest	0	0
Nonaccrual loans	3,471,000	2,611,000
Total nonperforming loans	$ 3,471,000	$ 2,611,000