INVESTMENT SECURITIES - Amortized Cost of Investment Securities Held to Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Schedule of Held-to-maturity Securities [Line Items]
Total	$ 2,163,606	$ 2,184,497
Aaa
Schedule of Held-to-maturity Securities [Line Items]
Total	185,036
Aa1
Schedule of Held-to-maturity Securities [Line Items]
Total	159,923
Aa2
Schedule of Held-to-maturity Securities [Line Items]
Total	169,157
Aa3
Schedule of Held-to-maturity Securities [Line Items]
Total	133,379
A1
Schedule of Held-to-maturity Securities [Line Items]
Total	131,318
A2
Schedule of Held-to-maturity Securities [Line Items]
Total	16,837
A3
Schedule of Held-to-maturity Securities [Line Items]
Total	3,468
Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Total	1,364,488
State and municipal
Schedule of Held-to-maturity Securities [Line Items]
Total	1,097,848	$ 1,099,201
State and municipal | Aaa
Schedule of Held-to-maturity Securities [Line Items]
Total	114,449
State and municipal | Aa1
Schedule of Held-to-maturity Securities [Line Items]
Total	159,923
State and municipal | Aa2
Schedule of Held-to-maturity Securities [Line Items]
Total	169,157
State and municipal | Aa3
Schedule of Held-to-maturity Securities [Line Items]
Total	133,379
State and municipal | A1
Schedule of Held-to-maturity Securities [Line Items]
Total	131,318
State and municipal | A2
Schedule of Held-to-maturity Securities [Line Items]
Total	16,837
State and municipal | A3
Schedule of Held-to-maturity Securities [Line Items]
Total	3,468
State and municipal | Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Total	369,317
Other
Schedule of Held-to-maturity Securities [Line Items]
Total	1,065,758
Other | Aaa
Schedule of Held-to-maturity Securities [Line Items]
Total	70,587
Other | Aa1
Schedule of Held-to-maturity Securities [Line Items]
Total	0
Other | Aa2
Schedule of Held-to-maturity Securities [Line Items]
Total	0
Other | Aa3
Schedule of Held-to-maturity Securities [Line Items]
Total	0
Other | A1
Schedule of Held-to-maturity Securities [Line Items]
Total	0
Other | A2
Schedule of Held-to-maturity Securities [Line Items]
Total	0
Other | A3
Schedule of Held-to-maturity Securities [Line Items]
Total	0
Other | Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Total	$ 995,171