Note 5 - Debt Securities - Schedule of Unrealized Loss on Investments (Details) $ in Thousands	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Number of Securities in Loss Positions	395	385
Estimated Fair Value, Less than 12 Months	$ 82,129	$ 148,825
Unrealized Loss, Less than 12 Months	2,284	3,912
Estimated Fair Value, 12 Months or More	333,747	264,467
Unrealized Loss, 12 Months or More	40,286	36,056
Estimated Fair Value, Total	415,876	413,292
Unrealized Loss, Total	$ 42,570	$ 39,968
US Government Corporations and Agencies Securities [Member]
Number of Securities in Loss Positions	38	39
Estimated Fair Value, Less than 12 Months	$ 1,929	$ 11,809
Unrealized Loss, Less than 12 Months	4	287
Estimated Fair Value, 12 Months or More	18,013	9,329
Unrealized Loss, 12 Months or More	642	221
Estimated Fair Value, Total	19,942	21,138
Unrealized Loss, Total	$ 646	$ 508
Government Sponsored Agencies [Member]
Number of Securities in Loss Positions	140	133
Estimated Fair Value, Less than 12 Months	$ 35,647	$ 68,815
Unrealized Loss, Less than 12 Months	1,060	1,528
Estimated Fair Value, 12 Months or More	75,938	32,902
Unrealized Loss, 12 Months or More	5,588	3,343
Estimated Fair Value, Total	111,585	101,717
Unrealized Loss, Total	$ 6,648	$ 4,871
Nongovernment Sponsored Agencies [Member]
Number of Securities in Loss Positions	34	35
Estimated Fair Value, Less than 12 Months	$ 5,955	$ 27,804
Unrealized Loss, Less than 12 Months	736	1,493
Estimated Fair Value, 12 Months or More	58,633	40,274
Unrealized Loss, 12 Months or More	3,568	3,010
Estimated Fair Value, Total	64,588	68,078
Unrealized Loss, Total	$ 4,304	$ 4,503
Taxable State and Political Subdivisions General Obligations [Member]
Number of Securities in Loss Positions	54	54
Estimated Fair Value, Less than 12 Months	$ 0	$ 0
Unrealized Loss, Less than 12 Months	0	0
Estimated Fair Value, 12 Months or More	63,352	63,336
Unrealized Loss, 12 Months or More	14,978	14,995
Estimated Fair Value, Total	63,352	63,336
Unrealized Loss, Total	$ 14,978	$ 14,995
Taxable State and Political Subdivisions Various Tax Revenues [Member]
Number of Securities in Loss Positions	7	7
Estimated Fair Value, Less than 12 Months	$ 0	$ 0
Unrealized Loss, Less than 12 Months	0	0
Estimated Fair Value, 12 Months or More	8,605	8,558
Unrealized Loss, 12 Months or More	2,052	2,107
Estimated Fair Value, Total	8,605	8,558
Unrealized Loss, Total	$ 2,052	$ 2,107
Taxable State and Political Subdivisions Other Revenues [Member]
Number of Securities in Loss Positions	21	21
Estimated Fair Value, Less than 12 Months	$ 0	$ 1,530
Unrealized Loss, Less than 12 Months	0	56
Estimated Fair Value, 12 Months or More	22,020	18,854
Unrealized Loss, 12 Months or More	4,797	4,726
Estimated Fair Value, Total	22,020	20,384
Unrealized Loss, Total	$ 4,797	$ 4,782
Corporate Debt Securities [Member]
Number of Securities in Loss Positions	19	21
Estimated Fair Value, Less than 12 Months	$ 4,626	$ 6,758
Unrealized Loss, Less than 12 Months	44	341
Estimated Fair Value, 12 Months or More	19,089	18,310
Unrealized Loss, 12 Months or More	1,607	1,422
Estimated Fair Value, Total	23,715	25,068
Unrealized Loss, Total	$ 1,651	$ 1,763
Asset-Backed Securities [Member]
Number of Securities in Loss Positions	9	17
Estimated Fair Value, Less than 12 Months	$ 4,397	$ 23,823
Unrealized Loss, Less than 12 Months	9	110
Estimated Fair Value, 12 Months or More	7,219	9,961
Unrealized Loss, 12 Months or More	61	154
Estimated Fair Value, Total	11,616	33,784
Unrealized Loss, Total	$ 70	$ 264
Tax Exempt State and Political Subdivisions General Obligations [Member]
Number of Securities in Loss Positions	52	39
Estimated Fair Value, Less than 12 Months	$ 28,338	$ 7,479
Unrealized Loss, Less than 12 Months	419	69
Estimated Fair Value, 12 Months or More	41,116	43,626
Unrealized Loss, 12 Months or More	4,280	3,647
Estimated Fair Value, Total	69,454	51,105
Unrealized Loss, Total	$ 4,699	$ 3,716
Tax Exempt State and Political Subdivisions Other Revenues [Member]
Number of Securities in Loss Positions	21	19
Estimated Fair Value, Less than 12 Months	$ 1,237	$ 807
Unrealized Loss, Less than 12 Months	12	28
Estimated Fair Value, 12 Months or More	19,762	19,317
Unrealized Loss, 12 Months or More	2,713	2,431
Estimated Fair Value, Total	20,999	20,124
Unrealized Loss, Total	$ 2,725	$ 2,459