INVESTMENT SECURITIES - Schedule of Gross Unrealized Losses and Fair Value of Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Estimated Fair Value
Less than 12 months, estimated fair value	$ 871,706	$ 1,405,288
12 months or more, estimated fair value	584,961	27,331
Total estimated fair value	1,456,667	1,432,619
Unrealized Losses
Less than 12 months, unrealized losses	(28,919)	(56,816)
12 months or more, unrealized losses	(35,481)	(2,318)
Total unrealized losses	(64,400)	(59,134)
U.S. Treasuries
Estimated Fair Value
Less than 12 months, estimated fair value	522,853	725,250
12 months or more, estimated fair value	235,813	0
Total estimated fair value	758,666	725,250
Unrealized Losses
Less than 12 months, unrealized losses	(11,833)	(16,381)
12 months or more, unrealized losses	(8,883)	0
Total unrealized losses	(20,716)	(16,381)
U.S. government-sponsored agencies
Estimated Fair Value
Less than 12 months, estimated fair value	0	979
12 months or more, estimated fair value	972	0
Total estimated fair value	972	979
Unrealized Losses
Less than 12 months, unrealized losses	0	(57)
12 months or more, unrealized losses	(57)	0
Total unrealized losses	(57)	(57)
State, county and municipal securities
Estimated Fair Value
Less than 12 months, estimated fair value	19,141	27,438
12 months or more, estimated fair value	12,002	0
Total estimated fair value	31,143	27,438
Unrealized Losses
Less than 12 months, unrealized losses	(337)	(1,180)
12 months or more, unrealized losses	(776)	0
Total unrealized losses	(1,113)	(1,180)
Corporate debt securities
Estimated Fair Value
Less than 12 months, estimated fair value	867	13,271
12 months or more, estimated fair value	13,188	1,155
Total estimated fair value	14,055	14,426
Unrealized Losses
Less than 12 months, unrealized losses	(30)	(126)
12 months or more, unrealized losses	(730)	(270)
Total unrealized losses	(760)	(396)
SBA pool securities
Estimated Fair Value
Less than 12 months, estimated fair value	465	17,806
12 months or more, estimated fair value	23,198	9,329
Total estimated fair value	23,663	27,135
Unrealized Losses
Less than 12 months, unrealized losses	(28)	(1,298)
12 months or more, unrealized losses	(1,948)	(729)
Total unrealized losses	(1,976)	(2,027)
Mortgage-backed securities
Estimated Fair Value
Less than 12 months, estimated fair value	328,380	620,544
12 months or more, estimated fair value	299,788	16,847
Total estimated fair value	628,168	637,391
Unrealized Losses
Less than 12 months, unrealized losses	(16,691)	(37,774)
12 months or more, unrealized losses	(23,087)	(1,319)
Total unrealized losses	$ (39,778)	$ (39,093)