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INVESTMENT SECURITIES - Amortized Cost and Estimated Fair Value of Investment Securities Available for Sale (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,877,387		$ 1,708,196
Allowance for Credit Losses	(66)	$ (69)	(69)	$ (68)	$ (73)	$ (69)
Gross Unrealized Gains	14,738		2,171
Gross Unrealized Losses	(20,761)		(39,038)
Estimated Fair Value	1,871,298		1,671,260
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	702,156		800,860
Allowance for Credit Losses	0		0
Gross Unrealized Gains	6,709		669
Gross Unrealized Losses	(1,052)		(5,065)
Estimated Fair Value	707,813		796,464
U.S. government-sponsored agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,003		1,010
Allowance for Credit Losses	0		0
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(6)		(16)
Estimated Fair Value	997		994
State, county and municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	22,425		25,802
Allowance for Credit Losses	0		0
Gross Unrealized Gains	7		8
Gross Unrealized Losses	(765)		(1,070)
Estimated Fair Value	21,667		24,740
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	10,945		10,946
Allowance for Credit Losses	(66)		(69)
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(498)		(594)
Estimated Fair Value	10,381		10,283
SBA pool securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	61,566		72,036
Allowance for Credit Losses	0		0
Gross Unrealized Gains	77		0
Gross Unrealized Losses	(924)		(1,554)
Estimated Fair Value	60,719		70,482
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,079,292		797,542
Allowance for Credit Losses	0		0
Gross Unrealized Gains	7,945		1,494
Gross Unrealized Losses	(17,516)		(30,739)
Estimated Fair Value	$ 1,069,721		$ 768,297