INVESTMENTS - Estimated Fair Values of Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value
Total available-for-sale debt securities	$ 1,102,681	$ 1,214,538
Amortized Cost
Amortized Cost	1,220,819	1,366,843
Fair Value
Total held-to-maturity debt securities	200,411	220,123
Amortized Cost
Amortized Cost	236,165	259,452
U.S. treasuries and government agencies
Fair Value
One year or less	17,798	0
One to five years	79,129	93,622
Five to ten years	0	0
After ten years	0	0
Total available-for-sale debt securities	96,927	93,622
Amortized Cost
One year or less	17,979	0
One to five years	83,699	100,926
Five to ten years	0	0
After ten years	0	0
Amortized Cost	101,678	100,926
State and municipal
Fair Value
One year or less	22,345	8,694
One to five years	33,282	51,576
Five to ten years	46,355	28,806
After ten years	166,232	176,921
Total available-for-sale debt securities	268,214	265,997
Amortized Cost
One year or less	22,793	8,783
One to five years	34,288	53,948
Five to ten years	54,487	34,042
After ten years	199,937	225,746
Amortized Cost	311,505	322,519
Mortgage-backed and asset-backed
Fair Value
One year or less	20,814	7,622
One to five years	29,823	45,366
Five to ten years	256,924	303,697
After ten years	429,979	498,234
Total available-for-sale debt securities	737,540	854,919
Amortized Cost
One year or less	21,111	7,704
One to five years	30,666	46,802
Five to ten years	280,209	335,285
After ten years	475,650	553,607
Amortized Cost	807,636	943,398
Fair Value
One year or less	0	0
One to five years	0	0
Five to ten years	31,434	35,304
After ten years	168,977	184,819
Total held-to-maturity debt securities	200,411	220,123
Amortized Cost
One year or less	0	0
One to five years	0	0
Five to ten years	34,458	39,213
After ten years	201,707	220,239
Amortized Cost	$ 236,165	$ 259,452