Note 9 - Fair Values - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale	$ 337,032	$ 286,950
Fair Value, Recurring [Member]
Total assets measured at fair value	337,032	286,950
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Total assets measured at fair value	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Total assets measured at fair value	337,032	286,950
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Total assets measured at fair value	0	0
US Government Agencies Debt Securities [Member]
Debt Securities, Available-for-sale	31,811	38,733
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member]
Debt Securities, Available-for-sale	31,811	38,733
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale	0	0
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale	31,811	38,733
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale	0	0
US States and Political Subdivisions Debt Securities [Member]
Debt Securities, Available-for-sale	91,863	42,098
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member]
Debt Securities, Available-for-sale	91,863	42,098
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale	0	0
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale	91,863	42,098
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale	0	0
Residential Mortgage Backed Securities and Collateralized Mortgage Obligations [Member]
Debt Securities, Available-for-sale	165,692	180,835
Residential Mortgage Backed Securities and Collateralized Mortgage Obligations [Member] | Fair Value, Recurring [Member]
Debt Securities, Available-for-sale	165,692	180,835
Residential Mortgage Backed Securities and Collateralized Mortgage Obligations [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale	0	0
Residential Mortgage Backed Securities and Collateralized Mortgage Obligations [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale	165,692	180,835
Residential Mortgage Backed Securities and Collateralized Mortgage Obligations [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale	0	0
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale	19,577	19,307
Commercial Mortgage Backed Securities [Member] | Fair Value, Recurring [Member]
Debt Securities, Available-for-sale	19,577	19,307
Commercial Mortgage Backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale	0	0
Commercial Mortgage Backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale	19,577	19,307
Commercial Mortgage Backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale	0	0
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale		2,966
Corporate Debt Securities [Member] | Fair Value, Recurring [Member]
Debt Securities, Available-for-sale		2,966
Corporate Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale		0
Corporate Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale		2,966
Corporate Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale		0
Asset-backed Securities [Member]
Debt Securities, Available-for-sale	28,089	3,011
Asset-backed Securities [Member] | Fair Value, Recurring [Member]
Debt Securities, Available-for-sale	28,089	3,011
Asset-backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale	0	0
Asset-backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale	28,089	3,011
Asset-backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale	$ 0	$ 0