INVESTMENTS - Estimated Fair Values of Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Fair Value
Total available-for-sale debt securities	$ 1,149,056	$ 1,102,681
Amortized Cost
Total available-for-sale debt securities	1,239,762	1,220,819
Fair Value
Total held-to-maturity debt securities	189,853	200,411
Amortized Cost
Total held-to-maturity debt securities	220,296	236,165
U.S. treasuries and government agencies
Fair Value
One year or less	36,945	17,798
One to five years	47,862	79,129
Five to ten years	0	0
After ten years	0	0
Total available-for-sale debt securities	84,807	96,927
Amortized Cost
One year or less	37,703	17,979
One to five years	49,534	83,699
Five to ten years	0	0
After ten years	0	0
Total available-for-sale debt securities	87,237	101,678
State and municipal
Fair Value
One year or less	28,604	22,345
One to five years	26,274	33,282
Five to ten years	57,006	46,355
After ten years	153,305	166,232
Total available-for-sale debt securities	265,189	268,214
Amortized Cost
One year or less	28,708	22,793
One to five years	27,069	34,288
Five to ten years	65,025	54,487
After ten years	183,042	199,937
Total available-for-sale debt securities	303,844	311,505
Mortgage-backed and asset-backed
Fair Value
One year or less	27,138	20,814
One to five years	21,587	29,823
Five to ten years	265,069	256,924
After ten years	485,266	429,979
Total available-for-sale debt securities	799,060	737,540
Amortized Cost
One year or less	27,224	21,111
One to five years	21,922	30,666
Five to ten years	281,025	280,209
After ten years	518,510	475,650
Total available-for-sale debt securities	848,681	807,636
Fair Value
One year or less	0	0
One to five years	0	0
Five to ten years	28,886	31,434
After ten years	160,967	168,977
Total held-to-maturity debt securities	189,853	200,411
Amortized Cost
One year or less	0	0
One to five years	0	0
Five to ten years	31,051	34,458
After ten years	189,245	201,707
Total held-to-maturity debt securities	$ 220,296	$ 236,165