INVESTMENTS - Summary of Investment Securities by Estimated Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Held-to-Maturity Amortized Cost
Amortized Cost	$ 38,321	$ 58,545
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	32,900	54,334
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	5,098,396	4,182,075
Available-for-Sale Market Value
Investment securities available-for-sale	4,635,304	3,971,932
One Year or Less [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	495
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	493
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	37,621
Available-for-Sale Market Value
Investment securities available-for-sale	37,493
After One Year Through Five Years [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	5,438
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	5,348
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	81,754
Available-for-Sale Market Value
Investment securities available-for-sale	72,700
After Five Years Through Ten Years [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	263,969
Available-for-Sale Market Value
Investment securities available-for-sale	229,926
After Ten Years [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	1,254
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	1,031
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	678,645
Available-for-Sale Market Value
Investment securities available-for-sale	579,756
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	2,002,626	1,607,916
Available-for-Sale Market Value
Investment securities available-for-sale	1,803,283	1,549,414
Commercial Mortgage Backed Securities [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	25,732	27,373
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	21,336	23,981
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	425,734	394,129
Available-for-Sale Market Value
Investment securities available-for-sale	395,078	381,600
Collateralized Mortgage Backed Securities [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	5,402	6,088
Held-to-Maturity Market Value
Debt Securities, Held-to-maturity, Fair Value	4,692	5,589
Available-for-Sale Amortized Cost
Debt Securities, Available-for-sale, Amortized Cost	1,084,939	741,819
Available-for-Sale Market Value
Investment securities available-for-sale	1,006,138	709,237
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	523,108	568,366
Available-for-Sale Market Value
Investment securities available-for-sale	$ 510,930	$ 556,544