INVESTMENTS - Summary of Investment Securities by Estimated Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Held-to-Maturity Amortized Cost
Amortized Cost	$ 79,542	$ 80,321
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	70,850	71,688
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	3,221,380	3,382,604
Available-for-Sale Market Value
Investment securities available-for-sale	2,850,667	3,021,126
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	10,537
Available-for-Sale Market Value
Investment securities available-for-sale	10,514
After One Year Through Five Years [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	5,048
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	5,077
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	159,964
Available-for-Sale Market Value
Investment securities available-for-sale	146,109
After Five Years Through Ten Years [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	32,733
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	29,637
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	225,990
Available-for-Sale Market Value
Investment securities available-for-sale	193,606
After Ten Years [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	1,678
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	1,454
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	565,924
Available-for-Sale Market Value
Investment securities available-for-sale	465,093
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	839,802	744,546
Available-for-Sale Market Value
Investment securities available-for-sale	742,226	661,048
Commercial Mortgage Backed Securities [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	32,286	32,926
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	27,547	28,298
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	428,261	543,134
Available-for-Sale Market Value
Investment securities available-for-sale	392,701	507,230
Collateralized Mortgage Backed Securities [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	7,797	7,970
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	7,135	7,431
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	429,785	478,744
Available-for-Sale Market Value
Investment securities available-for-sale	371,762	418,648
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	561,117	600,055
Available-for-Sale Market Value
Investment securities available-for-sale	$ 528,656	$ 560,248