INVESTMENT SECURITIES - Amortized Cost of Investment Securities Held to Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Schedule of Held-to-maturity Securities [Line Items]
Total	$ 2,108,894	$ 2,184,497
Aaa
Schedule of Held-to-maturity Securities [Line Items]
Total	1,132,647
Aa1
Schedule of Held-to-maturity Securities [Line Items]
Total	160,281
Aa2
Schedule of Held-to-maturity Securities [Line Items]
Total	177,858
Aa3
Schedule of Held-to-maturity Securities [Line Items]
Total	112,393
A1
Schedule of Held-to-maturity Securities [Line Items]
Total	141,608
A2
Schedule of Held-to-maturity Securities [Line Items]
Total	20,313
Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Total	363,794
U.S. Government-sponsored agency securities
Schedule of Held-to-maturity Securities [Line Items]
Total	361,335	374,002
U.S. Government-sponsored agency securities | Aaa
Schedule of Held-to-maturity Securities [Line Items]
Total	361,335
U.S. Government-sponsored agency securities | Aa1
Schedule of Held-to-maturity Securities [Line Items]
Total	0
U.S. Government-sponsored agency securities | Aa2
Schedule of Held-to-maturity Securities [Line Items]
Total	0
U.S. Government-sponsored agency securities | Aa3
Schedule of Held-to-maturity Securities [Line Items]
Total	0
U.S. Government-sponsored agency securities | A1
Schedule of Held-to-maturity Securities [Line Items]
Total	0
U.S. Government-sponsored agency securities | A2
Schedule of Held-to-maturity Securities [Line Items]
Total	0
U.S. Government-sponsored agency securities | Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Total	0
State and municipal
Schedule of Held-to-maturity Securities [Line Items]
Total	1,087,980	1,099,201
State and municipal | Aaa
Schedule of Held-to-maturity Securities [Line Items]
Total	113,233
State and municipal | Aa1
Schedule of Held-to-maturity Securities [Line Items]
Total	160,281
State and municipal | Aa2
Schedule of Held-to-maturity Securities [Line Items]
Total	177,858
State and municipal | Aa3
Schedule of Held-to-maturity Securities [Line Items]
Total	112,393
State and municipal | A1
Schedule of Held-to-maturity Securities [Line Items]
Total	141,608
State and municipal | A2
Schedule of Held-to-maturity Securities [Line Items]
Total	20,313
State and municipal | Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Total	362,294
U.S. Government-sponsored mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Total	658,079	$ 709,794
U.S. Government-sponsored mortgage-backed securities | Aaa
Schedule of Held-to-maturity Securities [Line Items]
Total	658,079
U.S. Government-sponsored mortgage-backed securities | Aa1
Schedule of Held-to-maturity Securities [Line Items]
Total	0
U.S. Government-sponsored mortgage-backed securities | Aa2
Schedule of Held-to-maturity Securities [Line Items]
Total	0
U.S. Government-sponsored mortgage-backed securities | Aa3
Schedule of Held-to-maturity Securities [Line Items]
Total	0
U.S. Government-sponsored mortgage-backed securities | A1
Schedule of Held-to-maturity Securities [Line Items]
Total	0
U.S. Government-sponsored mortgage-backed securities | A2
Schedule of Held-to-maturity Securities [Line Items]
Total	0
U.S. Government-sponsored mortgage-backed securities | Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Total	0
Foreign investment
Schedule of Held-to-maturity Securities [Line Items]
Total	1,500
Foreign investment | Aaa
Schedule of Held-to-maturity Securities [Line Items]
Total	0
Foreign investment | Aa1
Schedule of Held-to-maturity Securities [Line Items]
Total	0
Foreign investment | Aa2
Schedule of Held-to-maturity Securities [Line Items]
Total	0
Foreign investment | Aa3
Schedule of Held-to-maturity Securities [Line Items]
Total	0
Foreign investment | A1
Schedule of Held-to-maturity Securities [Line Items]
Total	0
Foreign investment | A2
Schedule of Held-to-maturity Securities [Line Items]
Total	0
Foreign investment | Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Total	$ 1,500