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INVESTMENTS (Summary of Amortized Costs and Estimated Fair Values of Available-For-Sale Securities) (Details) - USD ($) $ in Thousands | Sep. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost, Total | $ 705,019 | $ 796,960
Available-for-sale securities, at fair value (amortized cost of $705,019 and $796,960, respectively) | 589,003 | 695,875
Obligations of states and political subdivisions |  |
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost, Total | 42,652 | 49,678
Unrealized Gains | 0 | 11
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 1,983 | 463
Available-for-sale securities, at fair value (amortized cost of $705,019 and $796,960, respectively) | 40,669 | 49,226
MBS issued or guaranteed by U.S. government-sponsored enterprises |  |
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost, Total | 521,794 | 598,845
Unrealized Gains | 19 | 131
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 96,837 | 84,957
Available-for-sale securities, at fair value (amortized cost of $705,019 and $796,960, respectively) | 424,976 | 514,019
CMO issued or guaranteed by U.S. government-sponsored enterprises |  |
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost, Total | 118,890 | 122,760
Unrealized Gains | 25 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 14,099 | 13,413
Available-for-sale securities, at fair value (amortized cost of $705,019 and $796,960, respectively) | 104,816 | 109,347
Corporate bonds |  |
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost, Total | 21,683 | 25,677
Unrealized Gains | 0 | 3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 3,141 | 2,397
Available-for-sale securities, at fair value (amortized cost of $705,019 and $796,960, respectively) | 18,542 | 23,283
Total AFS debt securities |  |
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost, Total | 705,019 | 796,960
Unrealized Gains | 44 | 145
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 116,060 | 101,230
Available-for-sale securities, at fair value (amortized cost of $705,019 and $796,960, respectively) | $ 589,003 | $ 695,875

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- Definition 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). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-2 + Details
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