Note 3 - Investment Securities Available for Sale - Investment Securities With Unrealized Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Less than 12 months fair value	$ 158,264	$ 281,715
Less than 12 months unrealized losses	4,508	26,579
12 months or more fair value	227,219	113,148
12 months or more unrealized losses	43,717	28,204
Total fair value	385,483	394,863
Total unrealized losses	48,225	54,783
US Treasury Securities [Member]
Less than 12 months fair value	9,770	9,707
Less than 12 months unrealized losses	187	243
12 months or more fair value	0	0
12 months or more unrealized losses	0	0
Total fair value	9,770	9,707
Total unrealized losses	187	243
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Less than 12 months fair value	78,713	140,117
Less than 12 months unrealized losses	2,504	12,070
12 months or more fair value	115,974	54,017
12 months or more unrealized losses	18,871	11,989
Total fair value	194,687	194,134
Total unrealized losses	21,375	24,059
Commercial Mortgage Backed Securities Issued by US Government Agencies [Member]
Less than 12 months fair value	35,350	42,799
Less than 12 months unrealized losses	1,172	2,845
12 months or more fair value	49,192	42,363
12 months or more unrealized losses	10,788	9,859
Total fair value	84,542	85,162
Total unrealized losses	11,960	12,704
US States and Political Subdivisions Debt Securities [Member]
Less than 12 months fair value	34,431	89,092
Less than 12 months unrealized losses	645	11,421
12 months or more fair value	62,053	16,768
12 months or more unrealized losses	14,058	6,356
Total fair value	96,484	105,860
Total unrealized losses	$ 14,703	$ 17,777