Note 9 - Fair Values - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale	$ 579,664	$ 446,880
Fair Value, Recurring [Member]
Total assets measured at fair value	579,664	446,880
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	579,664	446,880
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	29,691	32,994
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member]
Debt Securities, Available-for-sale	29,691	32,994
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	29,691	32,994
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	136,467	108,366
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member]
Debt Securities, Available-for-sale	136,467	108,366
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	136,467	108,366
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	317,842	240,478
Residential Mortgage Backed Securities and Collateralized Mortgage Obligations [Member] | Fair Value, Recurring [Member]
Debt Securities, Available-for-sale	317,842	240,478
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	317,842	240,478
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	52,718	28,074
Commercial Mortgage Backed Securities [Member] | Fair Value, Recurring [Member]
Debt Securities, Available-for-sale	52,718	28,074
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	52,718	28,074
Commercial Mortgage Backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale	0	0
Asset-backed Securities [Member]
Debt Securities, Available-for-sale	42,946	36,968
Asset-backed Securities [Member] | Fair Value, Recurring [Member]
Debt Securities, Available-for-sale	42,946	36,968
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	42,946	36,968
Asset-backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale	$ 0	$ 0