Note 3 - Securities - Available-for-sale Debt Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Less than 12 months, number of securities	74	205
Less than 12 months, fair value	$ 81,912	$ 240,563
Less than 12 months, gross unrealized losses	$ 2,576	$ 19,668
12 months or longer, number of securities	312	192
12 months or longer, fair value	$ 384,049	$ 225,813
12 months or longer, gross unrealized losses	$ 50,757	$ 42,249
Total, number of securities	386	397
Total, fair value	$ 465,961	$ 466,376
Total, gross unrealized losses	$ 53,333	$ 61,917
US Treasury Securities [Member]
Less than 12 months, number of securities	0	0
Less than 12 months, fair value	$ 0	$ 0
Less than 12 months, gross unrealized losses	$ 0	$ 0
12 months or longer, number of securities	17	17
12 months or longer, fair value	$ 32,845	$ 32,134
12 months or longer, gross unrealized losses	$ 3,968	$ 4,667
Total, number of securities	17	17
Total, fair value	$ 32,845	$ 32,134
Total, gross unrealized losses	$ 3,968	$ 4,667
US States and Political Subdivisions Debt Securities [Member]
Less than 12 months, number of securities	36	128
Less than 12 months, fair value	$ 35,281	$ 146,932
Less than 12 months, gross unrealized losses	$ 547	$ 12,751
12 months or longer, number of securities	176	94
12 months or longer, fair value	$ 178,908	$ 69,872
12 months or longer, gross unrealized losses	$ 22,933	$ 16,801
Total, number of securities	212	222
Total, fair value	$ 214,189	$ 216,804
Total, gross unrealized losses	$ 23,480	$ 29,552
Residential Mortgage-Backed Securities [Member]
Less than 12 months, number of securities	1	16
Less than 12 months, fair value	$ 296	$ 26,826
Less than 12 months, gross unrealized losses	$ 12	$ 3,407
12 months or longer, number of securities	41	26
12 months or longer, fair value	$ 80,453	$ 53,581
12 months or longer, gross unrealized losses	$ 11,576	$ 9,763
Total, number of securities	42	42
Total, fair value	$ 80,749	$ 80,407
Total, gross unrealized losses	$ 11,588	$ 13,170
Commercial Mortgage-Backed Securities [Member]
Less than 12 months, number of securities	0	2
Less than 12 months, fair value	$ 0	$ 1,911
Less than 12 months, gross unrealized losses	$ 0	$ 94
12 months or longer, number of securities	3	1
12 months or longer, fair value	$ 3,358	$ 1,418
12 months or longer, gross unrealized losses	$ 282	$ 226
Total, number of securities	3	3
Total, fair value	$ 3,358	$ 3,329
Total, gross unrealized losses	$ 282	$ 320
Collateralized Mortgage-Backed Securities [Member]
Less than 12 months, number of securities	5	7
Less than 12 months, fair value	$ 7,208	$ 8,569
Less than 12 months, gross unrealized losses	$ 89	$ 219
12 months or longer, number of securities	8	7
12 months or longer, fair value	$ 12,655	$ 11,998
12 months or longer, gross unrealized losses	$ 2,274	$ 2,451
Total, number of securities	13	14
Total, fair value	$ 19,863	$ 20,567
Total, gross unrealized losses	$ 2,363	$ 2,670
Mortgage-Backed Securities, Issued by Private Enterprises [Member]
Less than 12 months, number of securities	17	29
Less than 12 months, fair value	$ 15,938	$ 27,705
Less than 12 months, gross unrealized losses	$ 477	$ 1,213
12 months or longer, number of securities	38	28
12 months or longer, fair value	$ 52,046	$ 42,819
12 months or longer, gross unrealized losses	$ 7,732	$ 6,928
Total, number of securities	55	57
Total, fair value	$ 67,984	$ 70,524
Total, gross unrealized losses	$ 8,209	$ 8,141
Corporate Debt Securities [Member]
Less than 12 months, number of securities	13	18
Less than 12 months, fair value	$ 15,921	$ 21,325
Less than 12 months, gross unrealized losses	$ 1,379	$ 1,805
12 months or longer, number of securities	17	11
12 months or longer, fair value	$ 16,119	$ 9,347
12 months or longer, gross unrealized losses	$ 1,691	$ 1,153
Total, number of securities	30	29
Total, fair value	$ 32,040	$ 30,672
Total, gross unrealized losses	$ 3,070	$ 2,958
Asset-Backed Securities [Member]
Less than 12 months, number of securities	2	5
Less than 12 months, fair value	$ 7,268	$ 7,295
Less than 12 months, gross unrealized losses	$ 72	$ 179
12 months or longer, number of securities	9	5
12 months or longer, fair value	$ 7,010	$ 3,988
12 months or longer, gross unrealized losses	$ 212	$ 172
Total, number of securities	11	10
Total, fair value	$ 14,278	$ 11,283
Total, gross unrealized losses	$ 284	$ 351
Negotiable Certificates of Deposit [Member]
Less than 12 months, number of securities	0	0
Less than 12 months, fair value	$ 0	$ 0
Less than 12 months, gross unrealized losses	$ 0	$ 0
12 months or longer, number of securities	3	3
12 months or longer, fair value	$ 655	$ 656
12 months or longer, gross unrealized losses	$ 89	$ 88
Total, number of securities	3	3
Total, fair value	$ 655	$ 656
Total, gross unrealized losses	$ 89	$ 88