Note 3 - Securities - Available-for-sale Debt Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Less than 12 months, number of securities	5	8
Less than 12 months, fair value	$ 4,551	$ 16,540
Less than 12 months, gross unrealized losses	$ 23	$ 249
12 months or longer, number of securities	357	361
12 months or longer, fair value	$ 411,816	$ 417,474
12 months or longer, gross unrealized losses	$ 51,432	$ 50,540
Total, number of securities	362	369
Total, fair value	$ 416,367	$ 434,014
Total, gross unrealized losses	$ 51,455	$ 50,789
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	$ 32,914	$ 33,177
12 months or longer, gross unrealized losses	$ 3,950	$ 3,675
Total, number of securities	17	17
Total, fair value	$ 32,914	$ 33,177
Total, gross unrealized losses	$ 3,950	$ 3,675
US States and Political Subdivisions Debt Securities [Member]
Less than 12 months, number of securities	0	1
Less than 12 months, fair value	$ 0	$ 2,121
Less than 12 months, gross unrealized losses	$ 0	$ 16
12 months or longer, number of securities	192	193
12 months or longer, fair value	$ 193,356	$ 195,153
12 months or longer, gross unrealized losses	$ 21,470	$ 20,421
Total, number of securities	192	194
Total, fair value	$ 193,356	$ 197,274
Total, gross unrealized losses	$ 21,470	$ 20,437
Residential Mortgage-Backed 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	42	42
12 months or longer, fair value	$ 72,803	$ 74,207
12 months or longer, gross unrealized losses	$ 13,062	$ 13,198
Total, number of securities	42	42
Total, fair value	$ 72,803	$ 74,207
Total, gross unrealized losses	$ 13,062	$ 13,198
Commercial Mortgage-Backed 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	3	3
12 months or longer, fair value	$ 3,370	$ 3,386
12 months or longer, gross unrealized losses	$ 234	$ 227
Total, number of securities	3	3
Total, fair value	$ 3,370	$ 3,386
Total, gross unrealized losses	$ 234	$ 227
Collateralized Mortgage-Backed Securities [Member]
Less than 12 months, number of securities	0	1
Less than 12 months, fair value	$ 0	$ 3,800
Less than 12 months, gross unrealized losses	$ 0	$ 54
12 months or longer, number of securities	12	12
12 months or longer, fair value	$ 15,440	$ 12,552
12 months or longer, gross unrealized losses	$ 2,712	$ 2,376
Total, number of securities	12	13
Total, fair value	$ 15,440	$ 16,352
Total, gross unrealized losses	$ 2,712	$ 2,430
Mortgage-Backed Securities, Issued by Private Enterprises [Member]
Less than 12 months, number of securities	5	3
Less than 12 months, fair value	$ 4,551	$ 5,670
Less than 12 months, gross unrealized losses	$ 23	$ 131
12 months or longer, number of securities	51	52
12 months or longer, fair value	$ 56,630	$ 58,846
12 months or longer, gross unrealized losses	$ 6,409	$ 6,707
Total, number of securities	56	55
Total, fair value	$ 61,181	$ 64,516
Total, gross unrealized losses	$ 6,432	$ 6,838
Corporate Debt Securities [Member]
Less than 12 months, number of securities	0	1
Less than 12 months, fair value	$ 0	$ 1,467
Less than 12 months, gross unrealized losses	$ 0	$ 33
12 months or longer, number of securities	29	29
12 months or longer, fair value	$ 30,564	$ 29,819
12 months or longer, gross unrealized losses	$ 3,486	$ 3,736
Total, number of securities	29	30
Total, fair value	$ 30,564	$ 31,286
Total, gross unrealized losses	$ 3,486	$ 3,769
Asset-Backed Securities [Member]
Less than 12 months, number of securities	0	2
Less than 12 months, fair value	$ 0	$ 3,482
Less than 12 months, gross unrealized losses	$ 0	$ 15
12 months or longer, number of securities	8	10
12 months or longer, fair value	$ 6,057	$ 9,660
12 months or longer, gross unrealized losses	$ 47	$ 130
Total, number of securities	8	12
Total, fair value	$ 6,057	$ 13,142
Total, gross unrealized losses	$ 47	$ 145
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	$ 682	$ 674
12 months or longer, gross unrealized losses	$ 62	$ 70
Total, number of securities	3	3
Total, fair value	$ 682	$ 674
Total, gross unrealized losses	$ 62	$ 70