INVESTMENTS - Estimated Fair Values of Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Fair Value
Total available-for-sale debt securities	$ 1,143,688	$ 1,214,538
Amortized Cost
Total available-for-sale debt securities	1,288,818	1,366,843
Fair Value
Total held-to-maturity debt securities	208,662	220,123
Amortized Cost
Total held-to-maturity debt securities	247,814	259,452
U.S. treasuries and government agencies
Fair Value
One year or less	14,580	0
One to five years	79,765	93,622
Five to ten years	0	0
After ten years	0	0
Total available-for-sale debt securities	94,345	93,622
Amortized Cost
One year or less	14,984	0
One to five years	86,315	100,926
Five to ten years	0	0
After ten years	0	0
Total available-for-sale debt securities	101,299	100,926
State and municipal
Fair Value
One year or less	6,799	8,694
One to five years	53,557	51,576
Five to ten years	36,343	28,806
After ten years	171,552	176,921
Total available-for-sale debt securities	268,251	265,997
Amortized Cost
One year or less	6,842	8,783
One to five years	55,926	53,948
Five to ten years	43,156	34,042
After ten years	212,891	225,746
Total available-for-sale debt securities	318,815	322,519
Mortgage-backed and asset-backed
Fair Value
One year or less	4,692	7,622
One to five years	47,004	45,366
Five to ten years	274,805	303,697
After ten years	454,591	498,234
Total available-for-sale debt securities	781,092	854,919
Amortized Cost
One year or less	4,744	7,704
One to five years	48,742	46,802
Five to ten years	305,295	335,285
After ten years	509,923	553,607
Total available-for-sale debt securities	868,704	943,398
Fair Value
One year or less	0	0
One to five years	0	0
Five to ten years	32,997	35,304
After ten years	175,665	184,819
Total held-to-maturity debt securities	208,662	220,123
Amortized Cost
One year or less	0	0
One to five years	0	0
Five to ten years	36,828	39,213
After ten years	210,986	220,239
Total held-to-maturity debt securities	$ 247,814	$ 259,452