BORROWINGS Borrowings - - Additional Information (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2020	Dec. 31, 2019
Carrying Value of Securities Sold under Repurchase Agreements and Deposits Received for Securities Loaned	$ 114,700	$ 90,200
Federal Funds Purchased	133,000	165,200
FHLB short-term borrowings	0	1,151,000
Long-term Debt	1,341,164	414,376
Secured Debt	$ 881,672	0
Long Term Debt Percentage in Basis Points	35
Convertible Subordinated Debt	$ 150,000
Subordinated Borrowing, Interest Rate	5.125%
Debt Instrument, Basis Spread on Variable Rate	0.05%
Subordinated debt	$ 120,000
Subordinated debt	$ 321,280	$ 170,967
Debt, Weighted Average Interest Rate	4.86%	4.97%
Advances from Federal Home Loan Banks	$ 138,424	$ 242,428
Federal Home Loan Bank	1.69%	1.94%
Weighted average rate on other long-term debt	0.00%	0.00%
Private Placement [Member]
Subordinated debt	$ 8,400
Debt, Weighted Average Interest Rate	6.00%
Long-term Debt [Member]
Subordinated Borrowing, Interest Rate	5.25%
Private Placement [Member]
DebtInstrumentMinimumCallablePeriod	5 years
Subordinated Debt [Member]
Subordinated debt	$ 49,500
Debt Instrument Maturity Period	30 years
DebtInstrumentMinimumCallablePeriod	5 years

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Represents the period at par after which the debt can be called.

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Long Term Debt Percentage shown in basis points

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Subordinated debt amount of original issue, excluding issue costs

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Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

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Carrying value of securities sold under agreements to repurchase and deposits received for securities loaned.

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Including the current and noncurrent portions, the carrying value of convertible subordinated debt, as of the balance sheet date, initially scheduled to be repaid after one year or beyond the normal operating cycle if longer. This form of debt can be exchanged for a specified amount of another security, typically the entity's common stock, at the option of the issuer or the holder, and places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Weighted average interest rate of debt outstanding.

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Amount of short term borrowing where a bank borrows, at the federal funds rate, from another bank.

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States the interest rate applicable to Federal Home Loan Bank advances outstanding as of the Balance Sheet date.

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Amount of advance from Federal Home Loan Bank (FHLBank) maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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Stated interest rate of the subordinated debt.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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