Note 10 - Fair Values - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale, Total	$ 345,533,000	$ 337,366,000
Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total	0	0
US Government Agencies Debt Securities [Member]
Debt Securities, Available-for-sale, Total	198,119,000	187,077,000
Collateralized Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale, Total	42,971,000	43,658,000
Municipal General Obligation Bonds [Member]
Debt Securities, Available-for-sale, Total	100,537,000	102,497,000
Municipal Revenue Bonds [Member]
Debt Securities, Available-for-sale, Total	3,406,000	3,634,000
Other Debt and Equity Securities [Member]
Debt Securities, Available-for-sale, Total	500,000	500,000
Fair Value, Recurring [Member]
Debt Securities, Available-for-sale, Total	345,533,000	337,366,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total	342,838,000	333,637,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total	2,695,000	3,729,000
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member]
Debt Securities, Available-for-sale, Total	198,119,000	187,077,000
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total	0	0
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total	198,119,000	187,077,000
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total	0	0
Fair Value, Recurring [Member] | Collateralized Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale, Total	42,971,000	43,658,000
Fair Value, Recurring [Member] | Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total	0	0
Fair Value, Recurring [Member] | Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total	42,971,000	43,658,000
Fair Value, Recurring [Member] | Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total	0	0
Fair Value, Recurring [Member] | Municipal General Obligation Bonds [Member]
Debt Securities, Available-for-sale, Total	100,537,000	102,497,000
Fair Value, Recurring [Member] | Municipal General Obligation Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total	0	0
Fair Value, Recurring [Member] | Municipal General Obligation Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total	97,842,000	98,768,000
Fair Value, Recurring [Member] | Municipal General Obligation Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total	2,695,000	3,729,000
Fair Value, Recurring [Member] | Municipal Revenue Bonds [Member]
Debt Securities, Available-for-sale, Total	3,406,000	3,634,000
Fair Value, Recurring [Member] | Municipal Revenue Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total	0	0
Fair Value, Recurring [Member] | Municipal Revenue Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total	3,406,000	3,634,000
Fair Value, Recurring [Member] | Municipal Revenue Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total	0	0
Fair Value, Recurring [Member] | Other Debt and Equity Securities [Member]
Debt Securities, Available-for-sale, Total	500,000	500,000
Fair Value, Recurring [Member] | Other Debt and Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total	0	0
Fair Value, Recurring [Member] | Other Debt and Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total	500,000	500,000
Fair Value, Recurring [Member] | Other Debt and Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total	$ 0	$ 0