INVESTMENT SECURITIES - Schedule of Maturities of Investment Securities Available-for-Sale and Held-to-Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Available for Sale, Amortized Cost
Within one year	$ 2,480	$ 0
After one year but within five years	97,525	86,224
After five years but within ten years	549,047	569,956
After ten years	3,795,624	3,848,162
Amortized Cost	4,444,676	4,504,342
Available for Sale, Fair Value
Within one year	2,415	0
After one year but within five years	92,024	82,387
After five years but within ten years	462,583	485,593
After ten years	3,177,207	3,278,557
Available-for-sale, fair value total	3,734,229	3,846,537
Held to Maturity, Amortized Cost
Within one year	0	0
After one year but within five years	11,930	10,932
After five years but within ten years	47,195	46,489
After ten years	990,690	1,001,144
Investment securities held-to-maturity, net	1,049,815	1,058,565
Held to Maturity, Fair Value
Within one year	0	0
After one year but within five years	11,741	10,856
After five years but within ten years	46,747	46,246
After ten years	891,239	928,829
Held-to-maturity, fair value total	$ 949,727	$ 985,931