INVESTMENTS - Summary of Investment Securities by Estimated Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Held-to-Maturity Amortized Cost
Amortized Cost	$ 82,372	$ 84,021
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	72,399	76,485
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	3,660,078	3,827,418
Available-for-Sale Market Value
Investment securities available-for-sale	3,249,404	3,409,648
One Year or Less [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	0
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	0
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	8,597
Available-for-Sale Market Value
Investment securities available-for-sale	8,498
After One Year Through Five Years [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	4,129
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	4,156
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	125,209
Available-for-Sale Market Value
Investment securities available-for-sale	115,469
After Five Years Through Ten Years [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	33,485
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	29,540
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	271,267
Available-for-Sale Market Value
Investment securities available-for-sale	236,710
After Ten Years [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	1,789
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	1,518
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	677,861
Available-for-Sale Market Value
Investment securities available-for-sale	572,753
Residential Mortgage Backed Securities [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	0	0
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	0	0
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	720,755	747,478
Available-for-Sale Market Value
Investment securities available-for-sale	625,024	650,063
Commercial Mortgage Backed Securities [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	34,151	35,363
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	29,314	31,249
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	639,464	676,934
Available-for-Sale Market Value
Investment securities available-for-sale	591,595	629,562
Collateralized Mortgage Backed Securities [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	8,818	9,280
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	7,871	8,453
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	506,674	538,970
Available-for-Sale Market Value
Investment securities available-for-sale	442,184	477,712
Asset-backed Securities [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	0	0
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	0	0
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	710,251	772,261
Available-for-Sale Market Value
Investment securities available-for-sale	$ 657,171	$ 711,325