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SECURITIES (Amortized Cost of AFS Securities by Security Type and Credit Rating) (Details) - USD ($) $ in Thousands | Mar. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | $ 1,900,313 | $ 1,893,427
Standard & Poor's AAA/AA/A | Moody's AAA/AA/A |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 588,018 |
Standard & Poor's BBB/BB/B | Moody's BBB/BB/B |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 23,886 |
Standard Poors Not Rated - Agency [Member] | Moody's Not Rated - Agency [Member] |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 1,170,237 |
Standard Poors Not Rated - Non-Agency [Member] | Moody's Not Rated - Non-Agency [Member] |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 118,172 |
U.S. government and agency securities |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 17,631 | 21,149
U.S. government and agency securities | Standard & Poor's AAA/AA/A | Moody's AAA/AA/A |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 2,497 |
U.S. government and agency securities | Standard & Poor's BBB/BB/B | Moody's BBB/BB/B |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 0 |
U.S. government and agency securities | Standard Poors Not Rated - Agency [Member] | Moody's Not Rated - Agency [Member] |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 15,134 |
U.S. government and agency securities | Standard Poors Not Rated - Non-Agency [Member] | Moody's Not Rated - Non-Agency [Member] |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 0 |
Obligations of states and political subdivisions |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 515,914 | 421,344
Obligations of states and political subdivisions | Standard & Poor's AAA/AA/A | Moody's AAA/AA/A |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 514,374 |
Obligations of states and political subdivisions | Standard & Poor's BBB/BB/B | Moody's BBB/BB/B |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 1,033 |
Obligations of states and political subdivisions | Standard Poors Not Rated - Agency [Member] | Moody's Not Rated - Agency [Member] |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 0 |
Obligations of states and political subdivisions | Standard Poors Not Rated - Non-Agency [Member] | Moody's Not Rated - Non-Agency [Member] |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 507 |
Corporate and other bonds |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 122,232 | 134,342
Corporate and other bonds | Standard & Poor's AAA/AA/A | Moody's AAA/AA/A |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 32,288 |
Corporate and other bonds | Standard & Poor's BBB/BB/B | Moody's BBB/BB/B |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 22,853 |
Corporate and other bonds | Standard Poors Not Rated - Agency [Member] | Moody's Not Rated - Agency [Member] |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 0 |
Corporate and other bonds | Standard Poors Not Rated - Non-Agency [Member] | Moody's Not Rated - Non-Agency [Member] |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 67,091 |
Total mortgage-back securities |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 1,241,446 | 1,313,513
Total mortgage-back securities | Standard & Poor's AAA/AA/A | Moody's AAA/AA/A |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 38,859 |
Total mortgage-back securities | Standard & Poor's BBB/BB/B | Moody's BBB/BB/B |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 0 |
Total mortgage-back securities | Standard Poors Not Rated - Agency [Member] | Moody's Not Rated - Agency [Member] |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 1,153,495 |
Total mortgage-back securities | Standard Poors Not Rated - Non-Agency [Member] | Moody's Not Rated - Non-Agency [Member] |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 49,092 |
Other securities |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 3,090 | $ 3,079
Other securities | Standard & Poor's AAA/AA/A | Moody's AAA/AA/A |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 0 |
Other securities | Standard & Poor's BBB/BB/B | Moody's BBB/BB/B |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 0 |
Other securities | Standard Poors Not Rated - Agency [Member] | Moody's Not Rated - Agency [Member] |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | 1,608 |
Other securities | Standard Poors Not Rated - Non-Agency [Member] | Moody's Not Rated - Non-Agency [Member] |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |
AFS Securities, Amortized Cost | $ 1,482 |

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