INVESTMENT SECURITIES - Amortized Cost of Investment Securities Held to Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Schedule of Held-to-maturity Securities [Line Items]
Total	$ 2,240,374	$ 2,287,372
Aaa
Schedule of Held-to-maturity Securities [Line Items]
Total	185,397
Aa1
Schedule of Held-to-maturity Securities [Line Items]
Total	149,970
Aa2
Schedule of Held-to-maturity Securities [Line Items]
Total	185,019
Aa3
Schedule of Held-to-maturity Securities [Line Items]
Total	133,560
A1
Schedule of Held-to-maturity Securities [Line Items]
Total	131,306
A2
Schedule of Held-to-maturity Securities [Line Items]
Total	10,171
A3
Schedule of Held-to-maturity Securities [Line Items]
Total	10,122
Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Total	1,434,829
State and municipal
Schedule of Held-to-maturity Securities [Line Items]
Total	1,111,355	$ 1,117,552
State and municipal | Aaa
Schedule of Held-to-maturity Securities [Line Items]
Total	114,813
State and municipal | Aa1
Schedule of Held-to-maturity Securities [Line Items]
Total	149,970
State and municipal | Aa2
Schedule of Held-to-maturity Securities [Line Items]
Total	185,019
State and municipal | Aa3
Schedule of Held-to-maturity Securities [Line Items]
Total	133,560
State and municipal | A1
Schedule of Held-to-maturity Securities [Line Items]
Total	131,306
State and municipal | A2
Schedule of Held-to-maturity Securities [Line Items]
Total	10,171
State and municipal | A3
Schedule of Held-to-maturity Securities [Line Items]
Total	10,122
State and municipal | Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Total	376,394
Other
Schedule of Held-to-maturity Securities [Line Items]
Total	1,129,019
Other | Aaa
Schedule of Held-to-maturity Securities [Line Items]
Total	70,584
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	$ 1,058,435