Note 4 - Investment Securities - Available-for-sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Securities available-for-sale, amortized cost	$ 1,297,977	$ 1,190,379
Securities available-for-sale, unrealized gains	349	5,281
Securities available-for-sale, unrealized losses	(153,709)	(15,362)
Securities available-for-sale, fair value	1,144,617	1,180,298
US Treasury Securities and US Government Agencies Debt Securities [Member]
Securities available-for-sale, amortized cost	122,966	123,753
Securities available-for-sale, unrealized gains	0	0
Securities available-for-sale, unrealized losses	(7,927)	(1,252)
Securities available-for-sale, fair value	115,039	122,501
US Government-sponsored Enterprises Debt Securities [Member]
Securities available-for-sale, amortized cost	149,773	132,760
Securities available-for-sale, unrealized gains	290	2,497
Securities available-for-sale, unrealized losses	(6,437)	(236)
Securities available-for-sale, fair value	143,626	135,021
Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available-for-sale, amortized cost	874,265	857,283
Securities available-for-sale, unrealized gains	58	2,495
Securities available-for-sale, unrealized losses	(121,585)	(13,154)
Securities available-for-sale, fair value	752,738	846,624
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale, amortized cost	145,016	75,488
Securities available-for-sale, unrealized gains	1	289
Securities available-for-sale, unrealized losses	(17,418)	(702)
Securities available-for-sale, fair value	127,599	75,075
Other Debt Obligations [Member]
Securities available-for-sale, amortized cost	5,957	1,095
Securities available-for-sale, unrealized gains	0	0
Securities available-for-sale, unrealized losses	(342)	(18)
Securities available-for-sale, fair value	$ 5,615	$ 1,077

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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