INVESTMENT SECURITIES - Schedule of Maturities of Investment Securities Available-for-Sale and Held-to-Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Available for Sale, Amortized Cost
Within one year	$ 46,291	$ 16,833
After one year but within five years	158,811	147,157
After five years but within ten years	483,677	487,921
After ten years	3,340,576	3,566,355
Amortized Cost	4,029,355	4,218,266
Available for Sale, Fair Value
Within one year	45,761	16,698
After one year but within five years	150,121	138,870
After five years but within ten years	429,792	409,908
After ten years	2,876,485	2,945,172
Fair value	3,502,159	3,510,648
Held to Maturity, Amortized Cost
Within one year	1,420	0
After one year but within five years	19,175	16,727
After five years but within ten years	68,957	51,671
After ten years	890,152	946,770
Amortized cost	979,704	1,015,168
Held to Maturity, Fair Value
Within one year	1,420	0
After one year but within five years	19,163	16,444
After five years but within ten years	68,957	50,451
After ten years	796,642	828,616
Fair value	$ 886,182	$ 895,511