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BORROWINGS, Contractual Maturity on Borrowings (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2015 | Dec. 31, 2014
Debt Instrument [Line Items] |  |
Carrying value | $ 403,446 | $ 440,122
Weighted-average rate at period end | 1.05% |
Weighted-average interest rate on borrowings during period | 0.82% | 0.89%
Federal Home Loan Bank Overnight Advance [Member] |  |
Debt Instrument [Line Items] |  |
Carrying value | $ 301,300 | $ 338,000
Federal Home Loan Bank Overnight Advance [Member] | January 4, 2016 [Member] |  |
Debt Instrument [Line Items] |  |
Carrying value | $ 301,300 |
Weighted-average rate at period end | 0.52% |
Subordinated Debt Held By Unconsolidated Subsidiary Trust [Member] |  |
Debt Instrument [Line Items] |  |
Carrying value | $ 102,146 | $ 102,122
Subordinated Debt Held By Unconsolidated Subsidiary Trust [Member] | July 31, 2031 [Member] |  |
Debt Instrument [Line Items] |  |
Carrying value | $ 24,826 |
Weighted-average rate at period end | 3.91% |
Subordinated Debt Held By Unconsolidated Subsidiary Trust [Member] | December 15, 2036 [Member] |  |
Debt Instrument [Line Items] |  |
Carrying value | $ 77,320 |
Weighted-average rate at period end | 2.16% |

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