SECURITIES - Summary of Amortized Cost and Fair Value of Available-For-Sale Securities and Held-To-Maturity Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Available-for-sale securities:
Amortized Cost	$ 1,326,894	$ 1,418,337
Gross Unrealized Gains	221	672
Gross Unrealized Losses	185,144	161,908
Securities available-for-sale	1,141,971	1,257,101
Held-to-maturity:
Amortized Cost	658,524	691,484
Gross Unrealized Gains	96	4,532
Gross Unrealized Losses	76,028	53,919
Estimated Fair Value	582,592	642,097
U.S. Treasury
Available-for-sale securities:
Amortized Cost	135,648	135,752
Gross Unrealized Gains	0	0
Gross Unrealized Losses	10,954	11,898
Securities available-for-sale	124,694	123,854
Held-to-maturity:
Amortized Cost	89,687	109,631
Gross Unrealized Gains	0	0
Gross Unrealized Losses	4,256	5,175
Estimated Fair Value	85,431	104,456
Obligations of U.S. government agencies and sponsored entities
Available-for-sale securities:
Amortized Cost	147,347	163,054
Gross Unrealized Gains	1	3
Gross Unrealized Losses	21,984	18,688
Securities available-for-sale	125,364	144,369
Held-to-maturity:
Amortized Cost	33,656	33,789
Gross Unrealized Gains	0	0
Gross Unrealized Losses	2,781	2,153
Estimated Fair Value	30,875	31,636
Tax-exempt and taxable obligations of states and municipal subdivisions
Available-for-sale securities:
Amortized Cost	494,334	519,190
Gross Unrealized Gains	168	598
Gross Unrealized Losses	74,824	61,931
Securities available-for-sale	419,678	457,857
Held-to-maturity:
Amortized Cost	246,611	247,467
Gross Unrealized Gains	96	4,525
Gross Unrealized Losses	28,288	13,699
Estimated Fair Value	218,419	238,293
Mortgage-backed securities - residential
Available-for-sale securities:
Amortized Cost	307,867	341,272
Gross Unrealized Gains	4	11
Gross Unrealized Losses	46,914	42,041
Securities available-for-sale	260,957	299,242
Held-to-maturity:
Amortized Cost	144,991	156,119
Gross Unrealized Gains	0	0
Gross Unrealized Losses	21,971	17,479
Estimated Fair Value	123,020	138,640
Mortgage-backed securities - commercial
Available-for-sale securities:
Amortized Cost	199,065	215,200
Gross Unrealized Gains	48	60
Gross Unrealized Losses	26,114	24,363
Securities available-for-sale	172,999	190,897
Held-to-maturity:
Amortized Cost	133,579	134,478
Gross Unrealized Gains	0	7
Gross Unrealized Losses	17,028	13,798
Estimated Fair Value	116,551	120,687
Corporate obligations
Available-for-sale securities:
Amortized Cost	41,633	43,869
Gross Unrealized Gains	0	0
Gross Unrealized Losses	4,354	2,987
Securities available-for-sale	37,279	40,882
Held-to-maturity:
Amortized Cost	10,000	10,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	1,704	1,615
Estimated Fair Value	8,296	$ 8,385
Other
Available-for-sale securities:
Amortized Cost	1,000
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Securities available-for-sale	$ 1,000