INVESTMENT SECURITIES - AFS and HTM Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Amortized Cost
Amortized Cost	$ 1,621,169	$ 1,585,334
Fair Value
Fair Value	1,528,051	1,483,042
Fair Value
Fair Value	1,521,621	$ 1,549,509
Excluding Mortgage-Backed Securities
Amortized Cost
Due within one year	3,000
Due after one year through five years	63,881
Due after five years through ten years	305,694
Due after ten years	538,676
Amortized Cost	911,251
Fair Value
Due within one year	2,938
Due after one year through five years	59,373
Due after five years through ten years	291,046
Due after ten years	522,453
Fair Value	875,810
Amortized Cost
Due within one year	0
Due after one year through five years	9,443
Due after five years through ten years	118,141
Due after ten years	1,275,508
Amortized Cost	1,403,092
Fair Value
Due within one year	0
Due after one year through five years	9,129
Due after five years through ten years	117,180
Due after ten years	1,150,198
Fair Value	$ 1,276,507