Note 7 - Fair Value Measurements - Assets Measured at Fair Value on Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Securities available for sale	$ 276,937	$ 255,844
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available for sale	118,149	108,237
Agency Collateralized Mortgage Obligations [Member]
Securities available for sale	15,194	16,028
US Government Agencies Debt Securities [Member]
Securities available for sale	70,437	68,662
Municipal Notes [Member]
Securities available for sale	72,946	62,843
Mutual Funds [Member]
Securities available for sale	211	74
Fair Value, Measurements, Recurring [Member]
Securities available for sale	276,937	255,844
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available for sale	118,149	108,237
Fair Value, Measurements, Recurring [Member] | Agency Collateralized Mortgage Obligations [Member]
Securities available for sale	15,194	16,028
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member]
Securities available for sale	70,437	68,662
Fair Value, Measurements, Recurring [Member] | Municipal Notes [Member]
Securities available for sale	72,946	62,843
Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Securities available for sale	211	74
Fair Value, Measurements, Nonrecurring [Member]
Impaired loans	3,521	3,622
Loans held for sale	1,000	4,507
Foreclosed real estate	3,882	4,674
Fair Value, Measurements, Nonrecurring [Member] | Residential Mortgage Segment [Member]
Impaired loans	2,926	2,060
Foreclosed real estate	304	226
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Segment [Member]
Impaired loans	297	100
Foreclosed real estate	3,528	4,448
Fair Value, Measurements, Nonrecurring [Member] | Commercial Business Segment [Member]
Impaired loans	55	231
Fair Value, Measurements, Nonrecurring [Member] | Home Equity and Second Mortgage [Member]
Impaired loans	243	14
Fair Value, Measurements, Nonrecurring [Member] | Other Consumer Segment [Member]
Impaired loans	0
Fair Value, Measurements, Nonrecurring [Member] | Land Segment [Member]
Impaired loans		1,217
Foreclosed real estate	50
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Securities available for sale	211	74
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available for sale	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Agency Collateralized Mortgage Obligations [Member]
Securities available for sale	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member]
Securities available for sale	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Municipal Notes [Member]
Securities available for sale	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Securities available for sale	211	74
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Impaired loans	0	0
Loans held for sale	0	0
Foreclosed real estate	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Residential Mortgage Segment [Member]
Impaired loans	0	0
Foreclosed real estate	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Segment [Member]
Impaired loans	0	0
Foreclosed real estate	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Business Segment [Member]
Impaired loans	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Home Equity and Second Mortgage [Member]
Impaired loans	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Other Consumer Segment [Member]
Impaired loans	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Land Segment [Member]
Impaired loans		0
Foreclosed real estate	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Securities available for sale	276,726	255,770
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available for sale	118,149	108,237
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Agency Collateralized Mortgage Obligations [Member]
Securities available for sale	15,194	16,028
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member]
Securities available for sale	70,437	68,662
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Municipal Notes [Member]
Securities available for sale	72,946	62,843
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Securities available for sale	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Impaired loans	0	0
Loans held for sale	1,000	4,507
Foreclosed real estate	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Residential Mortgage Segment [Member]
Impaired loans	0	0
Foreclosed real estate	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Segment [Member]
Impaired loans	0	0
Foreclosed real estate	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Business Segment [Member]
Impaired loans	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Home Equity and Second Mortgage [Member]
Impaired loans	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Other Consumer Segment [Member]
Impaired loans	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Land Segment [Member]
Impaired loans		0
Foreclosed real estate	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Securities available for sale	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available for sale	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Agency Collateralized Mortgage Obligations [Member]
Securities available for sale	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member]
Securities available for sale	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Municipal Notes [Member]
Securities available for sale	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Securities available for sale	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Impaired loans	3,521	3,622
Loans held for sale	0	0
Foreclosed real estate	3,882	4,674
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Residential Mortgage Segment [Member]
Impaired loans	2,926	2,060
Foreclosed real estate	304	226
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Segment [Member]
Impaired loans	297	100
Foreclosed real estate	3,528	4,448
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Business Segment [Member]
Impaired loans	55	231
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Home Equity and Second Mortgage [Member]
Impaired loans	243	14
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Other Consumer Segment [Member]
Impaired loans	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Land Segment [Member]
Impaired loans		$ 1,217
Foreclosed real estate	$ 50