SECURITIES - Amortized Cost and Fair Value of Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,613,672	$ 1,988,916
Gross Unrealized Gains	725	4,773
Gross Unrealized Losses	(199,445)	(186,103)
Fair Value	1,414,952	1,807,586
U.S. government and agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	409,152	433,417
Gross Unrealized Gains	129	90
Gross Unrealized Losses	(15,873)	(19,227)
Fair Value	393,408	414,280
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	258,901	580,076
Gross Unrealized Gains	545	4,319
Gross Unrealized Losses	(40,330)	(43,826)
Fair Value	219,116	540,569
Agency mortgage-backed pass-through securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	378,573	370,471
Gross Unrealized Gains	22	362
Gross Unrealized Losses	(50,401)	(42,032)
Fair Value	328,194	328,801
Agency collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	444,234	461,760
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(78,356)	(67,630)
Fair Value	365,878	394,130
Corporate bonds and other
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	122,812	143,192
Gross Unrealized Gains	29	2
Gross Unrealized Losses	(14,485)	(13,388)
Fair Value	$ 108,356	$ 129,806