Note 3 - Investment Securities Available for Sale - Investment Securities With Unrealized Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Less than 12 months fair value	$ 109,858	$ 69,763
Less than 12 months unrealized losses	1,222	725
12 months or more fair value	235,374	321,809
12 months or more unrealized losses	33,192	47,246
Total fair value	345,232	391,572
Total unrealized losses	34,414	47,971
US Treasury Securities [Member]
Less than 12 months fair value	0	0
Less than 12 months unrealized losses	0	0
12 months or more fair value	6,918	6,880
12 months or more unrealized losses	69	98
Total fair value	6,918	6,880
Total unrealized losses	69	98
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Less than 12 months fair value	68,116	43,924
Less than 12 months unrealized losses	694	279
12 months or more fair value	117,201	160,383
12 months or more unrealized losses	14,539	20,835
Total fair value	185,317	204,307
Total unrealized losses	15,233	21,114
Commercial Mortgage Backed Securities Issued by US Government Agencies [Member]
Less than 12 months fair value	33,867	16,533
Less than 12 months unrealized losses	457	295
12 months or more fair value	62,382	71,782
12 months or more unrealized losses	10,459	13,539
Total fair value	96,249	88,315
Total unrealized losses	10,916	13,834
US States and Political Subdivisions Debt Securities [Member]
Less than 12 months fair value	7,875	9,306
Less than 12 months unrealized losses	71	151
12 months or more fair value	48,873	82,764
12 months or more unrealized losses	8,125	12,774
Total fair value	56,748	92,070
Total unrealized losses	$ 8,196	$ 12,925