INVESTMENT SECURITIES - Amortized Cost and Approximate Fair Value of Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Available for sale securities
Amortized Cost	$ 1,742,679	$ 1,846,840
Gross Unrealized Gains	2,542	826
Gross Unrealized Losses	191,725	220,554
Fair Value	1,553,496	1,627,112
Held to maturity securities
Amortized Cost	2,108,894	2,184,497
Allowance for Credit Losses	245	245
Net Carrying Amount	2,108,649	2,184,252
Gross Unrealized Gains	1,157	1,625
Gross Unrealized Losses	287,045	315,748
Fair Value	1,823,006	1,870,374
U.S. Government-sponsored agency securities
Available for sale securities
Amortized Cost	97,670	111,521
Gross Unrealized Gains	0	0
Gross Unrealized Losses	12,637	16,214
Fair Value	85,033	95,307
Held to maturity securities
Amortized Cost	361,335	374,002
Allowance for Credit Losses	0	0
Net Carrying Amount	361,335	374,002
Gross Unrealized Gains	0	0
Gross Unrealized Losses	53,432	64,159
Fair Value	307,903	309,843
State and municipal
Available for sale securities
Amortized Cost	1,090,953	1,181,029
Gross Unrealized Gains	95	364
Gross Unrealized Losses	106,937	116,222
Fair Value	984,111	1,065,171
Held to maturity securities
Amortized Cost	1,087,980	1,099,201
Allowance for Credit Losses	245	245
Net Carrying Amount	1,087,735	1,098,956
Gross Unrealized Gains	1,157	1,625
Gross Unrealized Losses	151,227	152,113
Fair Value	937,910	948,713
U.S. Government-sponsored mortgage-backed securities
Available for sale securities
Amortized Cost	541,099	541,343
Gross Unrealized Gains	2,447	462
Gross Unrealized Losses	71,500	86,990
Fair Value	472,046	454,815
Held to maturity securities
Amortized Cost	658,079	709,794
Allowance for Credit Losses	0	0
Net Carrying Amount	658,079	709,794
Gross Unrealized Gains	0	0
Gross Unrealized Losses	82,382	99,448
Fair Value	575,697	610,346
Corporate obligations
Available for sale securities
Amortized Cost	12,957	12,947
Gross Unrealized Gains	0	0
Gross Unrealized Losses	651	1,128
Fair Value	12,306	11,819
Foreign investment
Held to maturity securities
Amortized Cost	1,500	1,500
Allowance for Credit Losses	0	0
Net Carrying Amount	1,500	1,500
Gross Unrealized Gains	0	0
Gross Unrealized Losses	4	28
Fair Value	$ 1,496	$ 1,472

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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