INVESTMENT SECURITIES - Amortized Cost of Investment Securities Held to Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Schedule of Held-to-maturity Securities [Line Items]
Total	$ 2,311,041	$ 2,180,047
Aaa
Schedule of Held-to-maturity Securities [Line Items]
Total	171,954
Aa1
Schedule of Held-to-maturity Securities [Line Items]
Total	162,890
Aa2
Schedule of Held-to-maturity Securities [Line Items]
Total	185,511
Aa3
Schedule of Held-to-maturity Securities [Line Items]
Total	135,285
A1
Schedule of Held-to-maturity Securities [Line Items]
Total	131,413
A2
Schedule of Held-to-maturity Securities [Line Items]
Total	10,167
A3
Schedule of Held-to-maturity Securities [Line Items]
Total	10,115
Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Total	1,503,706
State and municipal
Schedule of Held-to-maturity Securities [Line Items]
Total	1,114,312	$ 1,057,301
State and municipal | Aaa
Schedule of Held-to-maturity Securities [Line Items]
Total	101,372
State and municipal | Aa1
Schedule of Held-to-maturity Securities [Line Items]
Total	162,890
State and municipal | Aa2
Schedule of Held-to-maturity Securities [Line Items]
Total	185,511
State and municipal | Aa3
Schedule of Held-to-maturity Securities [Line Items]
Total	135,285
State and municipal | A1
Schedule of Held-to-maturity Securities [Line Items]
Total	131,413
State and municipal | A2
Schedule of Held-to-maturity Securities [Line Items]
Total	10,167
State and municipal | A3
Schedule of Held-to-maturity Securities [Line Items]
Total	10,115
State and municipal | Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Total	377,559
Other
Schedule of Held-to-maturity Securities [Line Items]
Total	1,196,729
Other | Aaa
Schedule of Held-to-maturity Securities [Line Items]
Total	70,582
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	$ 1,126,147