Note 5 - Retail Loans by Credit Quality (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	$ 733,078	$ 632,999
Total Retail Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	138,074	124,319
Performing Financial Instruments [Member] | Total Retail Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	136,964	123,871
Nonperforming Financial Instruments [Member] | Total Retail Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	1,110	448
Retail Portfolio Segment [Member] | Consumer Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	6,680	5,670
Retail Portfolio Segment [Member] | Family Residential Mortgages [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	55,818	47,124
Retail Portfolio Segment [Member] | Home Equity Loans and Lines [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	75,576	71,525
Retail Portfolio Segment [Member] | Performing Financial Instruments [Member] | Consumer Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	6,595	5,577
Retail Portfolio Segment [Member] | Performing Financial Instruments [Member] | Family Residential Mortgages [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	54,936	46,858
Retail Portfolio Segment [Member] | Performing Financial Instruments [Member] | Home Equity Loans and Lines [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	75,433	71,436
Retail Portfolio Segment [Member] | Nonperforming Financial Instruments [Member] | Consumer Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	85	93
Retail Portfolio Segment [Member] | Nonperforming Financial Instruments [Member] | Family Residential Mortgages [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	882	266
Retail Portfolio Segment [Member] | Nonperforming Financial Instruments [Member] | Home Equity Loans and Lines [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	$ 143	$ 89