INVESTMENTS - Amortized Cost and Estimated Fair Values of Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Available-for-sale debt securities:
Amortized Cost	$ 1,254,321	$ 1,220,819
Gross Unrealized Gains	196	182
Gross Unrealized Losses	(113,734)	(118,320)
Investments available-for-sale (at fair value)	1,140,783	1,102,681
Held-to-maturity debt securities
Amortized Cost	215,747	236,165
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(37,893)	(35,754)
Investments held-to-maturity (at fair value)	177,854	200,411
Total debt securities
Book value of debt securities pledged as collateral	1,470,068	1,456,984
Gross Unrealized Gains	196	182
Gross Unrealized Losses	(151,627)	(154,074)
Estimated Fair Value	1,318,637	1,303,092
U.S. treasuries and government agencies
Available-for-sale debt securities:
Amortized Cost	84,420	101,678
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2,106)	(4,751)
Investments available-for-sale (at fair value)	82,314	96,927
State and municipal
Available-for-sale debt securities:
Amortized Cost	281,837	311,505
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(46,904)	(43,292)
Investments available-for-sale (at fair value)	234,934	268,214
Mortgage-backed and asset-backed
Available-for-sale debt securities:
Amortized Cost	888,064	807,636
Gross Unrealized Gains	195	181
Gross Unrealized Losses	(64,724)	(70,277)
Investments available-for-sale (at fair value)	823,535	737,540
Held-to-maturity debt securities
Amortized Cost	215,747	236,165
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(37,893)	(35,754)
Investments held-to-maturity (at fair value)	$ 177,854	$ 200,411