Note 10 - Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Available-for-sale debt securities, at fair value	$ 274,114	$ 296,032
Equity securities, at fair value	903	891
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale debt securities, at fair value	132,124	152,187
Collateralized Mortgage Backed Securities [Member]
Available-for-sale debt securities, at fair value	21,112	23,934
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale debt securities, at fair value	2,807	2,913
Corporate Debt Securities [Member]
Available-for-sale debt securities, at fair value	4,993	4,936
Asset-backed Securities [Member]
Available-for-sale debt securities, at fair value	1,560	1,802
Negotiable Certificates of Deposit [Member]
Available-for-sale debt securities, at fair value	2,423	2,413
Fair Value, Recurring [Member]
Available-for-sale debt securities, at fair value	274,114	296,032
Equity securities, at fair value	903	891
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale debt securities, at fair value
Equity securities, at fair value	903	891
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale debt securities, at fair value	270,144	292,103
Equity securities, at fair value
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale debt securities, at fair value	3,970	3,929
Equity securities, at fair value
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale debt securities, at fair value	132,124	152,187
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale debt securities, at fair value
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale debt securities, at fair value	132,124	152,187
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale debt securities, at fair value
Fair Value, Recurring [Member] | Residential Mortgage [Member]
Available-for-sale debt securities, at fair value	33,952	34,207
Fair Value, Recurring [Member] | Residential Mortgage [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale debt securities, at fair value
Fair Value, Recurring [Member] | Residential Mortgage [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale debt securities, at fair value	33,952	34,207
Fair Value, Recurring [Member] | Residential Mortgage [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale debt securities, at fair value
Fair Value, Recurring [Member] | Commercial Loan [Member]
Available-for-sale debt securities, at fair value	75,143	73,640
Fair Value, Recurring [Member] | Commercial Loan [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale debt securities, at fair value
Fair Value, Recurring [Member] | Commercial Loan [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale debt securities, at fair value	75,143	73,640
Fair Value, Recurring [Member] | Commercial Loan [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale debt securities, at fair value
Fair Value, Recurring [Member] | Collateralized Mortgage Backed Securities [Member]
Available-for-sale debt securities, at fair value	21,112	23,934
Fair Value, Recurring [Member] | Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale debt securities, at fair value
Fair Value, Recurring [Member] | Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale debt securities, at fair value	21,112	23,934
Fair Value, Recurring [Member] | Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale debt securities, at fair value
Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale debt securities, at fair value	2,807	2,913
Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale debt securities, at fair value
Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale debt securities, at fair value	2,807	2,913
Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale debt securities, at fair value
Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Available-for-sale debt securities, at fair value	4,993	4,936
Fair Value, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale debt securities, at fair value
Fair Value, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale debt securities, at fair value	1,023	1,007
Fair Value, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale debt securities, at fair value	3,970	3,929
Fair Value, Recurring [Member] | Asset-backed Securities [Member]
Available-for-sale debt securities, at fair value	1,560	1,802
Fair Value, Recurring [Member] | Asset-backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale debt securities, at fair value
Fair Value, Recurring [Member] | Asset-backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale debt securities, at fair value	1,560	1,802
Fair Value, Recurring [Member] | Asset-backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale debt securities, at fair value
Fair Value, Recurring [Member] | Negotiable Certificates of Deposit [Member]
Available-for-sale debt securities, at fair value	2,423	2,413
Fair Value, Recurring [Member] | Negotiable Certificates of Deposit [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale debt securities, at fair value
Fair Value, Recurring [Member] | Negotiable Certificates of Deposit [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale debt securities, at fair value	2,423	2,413
Fair Value, Recurring [Member] | Negotiable Certificates of Deposit [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale debt securities, at fair value