INVESTMENT SECURITIES - Schedule of Gross Unrealized Losses and Fair Value of Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Estimated Fair Value
Less Than 12 Months	$ 245,513	$ 162,258
12 Months or More	1,159,293	1,154,553
Total	1,404,806	1,316,811
Unrealized Losses
Less Than 12 Months	(1,576)	(827)
12 Months or More	(48,506)	(43,909)
Total	(50,082)	(44,736)
U.S. Treasuries
Estimated Fair Value
Less Than 12 Months	133,526	159,667
12 Months or More	562,763	537,313
Total	696,289	696,980
Unrealized Losses
Less Than 12 Months	(1,129)	(827)
12 Months or More	(10,568)	(10,966)
Total	(11,697)	(11,793)
U.S. government-sponsored agencies
Estimated Fair Value
Less Than 12 Months	0	0
12 Months or More	980	985
Total	980	985
Unrealized Losses
Less Than 12 Months	0	0
12 Months or More	(40)	(38)
Total	(40)	(38)
State, county and municipal securities
Estimated Fair Value
Less Than 12 Months	5,362	1,923
12 Months or More	19,502	19,754
Total	24,864	21,677
Unrealized Losses
Less Than 12 Months	(10)	0
12 Months or More	(1,127)	(944)
Total	(1,137)	(944)
Corporate debt securities
Estimated Fair Value
Less Than 12 Months	499	500
12 Months or More	8,515	8,527
Total	9,014	9,027
Unrealized Losses
Less Than 12 Months	(1)	0
12 Months or More	(858)	(850)
Total	(859)	(850)
SBA pool securities
Estimated Fair Value
Less Than 12 Months	58,947	42
12 Months or More	19,333	21,267
Total	78,280	21,309
Unrealized Losses
Less Than 12 Months	(147)	0
12 Months or More	(1,590)	(1,519)
Total	(1,737)	(1,519)
Mortgage-backed securities
Estimated Fair Value
Less Than 12 Months	47,179	126
12 Months or More	548,200	566,707
Total	595,379	566,833
Unrealized Losses
Less Than 12 Months	(289)	0
12 Months or More	(34,323)	(29,592)
Total	$ (34,612)	$ (29,592)