Note 9 - Financial Assets Measured at Fair Value on a Recurring and Nonrecurring Basis (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	$ 10,482,000	$ 9,421,000
Debt securities available-for-sale	344,367,000	344,221,000
US Government Agencies Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities available-for-sale	69,359,000	68,409,000
US States and Political Subdivisions Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities available-for-sale	53,331,000	66,313,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities available-for-sale	133,039,000	125,913,000
Collateralized Mortgage Obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities available-for-sale	80,467,000	75,491,000
Pooled Trust Preferred Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities available-for-sale	112,000	116,000
Corporate Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities available-for-sale	8,059,000	7,979,000
Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	354,849,000	353,642,000
Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	2,324,000	3,060,000
Nonrecurring [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	2,320,000	3,055,000
Nonrecurring [Member] | Mortgage Servicing Rights [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	4,000	5,000
Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	10,482,000	9,421,000
Fair Value, Inputs, Level 1 [Member] | Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	10,482,000	9,421,000
Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities available-for-sale	344,255,000	344,105,000
Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities available-for-sale	69,359,000	68,409,000
Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities available-for-sale	53,331,000	66,313,000
Fair Value, Inputs, Level 2 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities available-for-sale	133,039,000	125,913,000
Fair Value, Inputs, Level 2 [Member] | Collateralized Mortgage Obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities available-for-sale	80,467,000	75,491,000
Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities available-for-sale	8,059,000	7,979,000
Fair Value, Inputs, Level 2 [Member] | Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	344,255,000	344,105,000
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities available-for-sale	112,000	116,000
Fair Value, Inputs, Level 3 [Member] | Pooled Trust Preferred Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities available-for-sale	112,000	116,000
Fair Value, Inputs, Level 3 [Member] | Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	112,000	116,000
Fair Value, Inputs, Level 3 [Member] | Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	2,324,000	3,060,000
Fair Value, Inputs, Level 3 [Member] | Nonrecurring [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	2,320,000	3,055,000
Fair Value, Inputs, Level 3 [Member] | Nonrecurring [Member] | Mortgage Servicing Rights [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	$ 4,000	$ 5,000