INVESTMENTS - Estimated Fair Values of Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Fair Value
Total available-for-sale debt securities	$ 1,101,846	$ 1,102,681
Amortized Cost
Total available-for-sale debt securities	1,226,968	1,220,819
Fair Value
Total held-to-maturity debt securities	187,389	200,411
Amortized Cost
Total held-to-maturity debt securities	226,233	236,165
U.S. treasuries and government agencies
Fair Value
One year or less	12,581	17,798
One to five years	70,378	79,129
Five to ten years	0	0
After ten years	0	0
Total available-for-sale debt securities	82,959	96,927
Amortized Cost
One year or less	12,893	17,979
One to five years	74,159	83,699
Five to ten years	0	0
After ten years	0	0
Total available-for-sale debt securities	87,052	101,678
State and municipal
Fair Value
One year or less	29,274	22,345
One to five years	29,372	33,282
Five to ten years	54,040	46,355
After ten years	149,209	166,232
Total available-for-sale debt securities	261,895	268,214
Amortized Cost
One year or less	29,516	22,793
One to five years	30,785	34,288
Five to ten years	64,547	54,487
After ten years	185,225	199,937
Total available-for-sale debt securities	310,073	311,505
Mortgage-backed and asset-backed
Fair Value
One year or less	35,077	20,814
One to five years	21,428	29,823
Five to ten years	269,833	256,924
After ten years	430,654	429,979
Total available-for-sale debt securities	756,992	737,540
Amortized Cost
One year or less	35,406	21,111
One to five years	22,031	30,666
Five to ten years	293,333	280,209
After ten years	479,073	475,650
Total available-for-sale debt securities	829,843	807,636
Fair Value
One year or less	0	0
One to five years	0	0
Five to ten years	29,041	31,434
After ten years	158,348	168,977
Total held-to-maturity debt securities	187,389	200,411
Amortized Cost
One year or less	0	0
One to five years	0	0
Five to ten years	32,194	34,458
After ten years	194,039	201,707
Total held-to-maturity debt securities	$ 226,233	$ 236,165