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FAIR VALUE OF FINANCIAL INSTRUMENTS, Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Financial Assets |  |
Derivative assets | $ 45,760 | $ 18,932
Financial Liabilities |  |
Derivative liabilities | 41,816 | 37,374
Recurring [Member] | Cash flow hedges |  |
Financial Assets |  |
Derivative assets | 3,944 |
Financial Liabilities |  |
Derivative liabilities |  | 18,442
Recurring [Member] | Freestanding derivatives |  |
Financial Assets |  |
Derivative assets | 41,816 | 30,596
Financial Liabilities |  |
Derivative liabilities | 41,816 | 30,596
Recurring [Member] | Level 2 Inputs [Member] | Cash flow hedges |  |
Financial Assets |  |
Derivative assets | 3,944 |
Financial Liabilities |  |
Derivative liabilities |  | 18,442
Recurring [Member] | Level 2 Inputs [Member] | Freestanding derivatives |  |
Financial Assets |  |
Derivative assets | 41,816 | 30,596
Financial Liabilities |  |
Derivative liabilities | 41,816 | 30,596
Nonrecurring [Member] |  |
Impaired Loans [Abstract] |  |
Fair value | 0 | 0
Agency Notes | Recurring [Member] |  |
Financial Assets |  |
Securities available-for-sale: | 69,570 | 47,421
Agency Notes | Recurring [Member] | Level 2 Inputs [Member] |  |
Financial Assets |  |
Securities available-for-sale: | 69,570 | 47,421
Treasury Securities | Recurring [Member] |  |
Financial Assets |  |
Securities available-for-sale: | 92,272 |
Treasury Securities | Recurring [Member] | Level 2 Inputs [Member] |  |
Financial Assets |  |
Securities available-for-sale: | 92,272 |
Corporate Securities | Recurring [Member] |  |
Financial Assets |  |
Securities available-for-sale: | 98,733 | 64,461
Corporate Securities | Recurring [Member] | Level 2 Inputs [Member] |  |
Financial Assets |  |
Securities available-for-sale: | 98,733 | 64,461
Pass-through MBS issued by GSEs | Recurring [Member] |  |
Financial Assets |  |
Securities available-for-sale: |  | 143,483
Mortgage-backed securities | 323,707 |
Pass-through MBS issued by GSEs | Recurring [Member] | Level 2 Inputs [Member] |  |
Financial Assets |  |
Securities available-for-sale: |  | 143,483
Mortgage-backed securities | 323,707 |
Agency Collateralized Mortgage Obligations ("CMOs") | Recurring [Member] |  |
Financial Assets |  |
Securities available-for-sale: | 522,822 | 283,496
Agency Collateralized Mortgage Obligations ("CMOs") | Recurring [Member] | Level 2 Inputs [Member] |  |
Financial Assets |  |
Securities available-for-sale: | 522,822 | 283,496
State and municipal obligations | Recurring [Member] |  |
Financial Assets |  |
Securities available-for-sale: | 45,389 |
State and municipal obligations | Recurring [Member] | Level 2 Inputs [Member] |  |
Financial Assets |  |
Securities available-for-sale: | $ 45,389 |
Domestic Equity Mutual Funds [Member] | Recurring [Member] |  |
Financial Assets |  |
Marketable equity securities (Registered Mutual Funds) |  | 1,769
Domestic Equity Mutual Funds [Member] | Recurring [Member] | Level 1 Inputs [Member] |  |
Financial Assets |  |
Marketable equity securities (Registered Mutual Funds) |  | 1,769
International Equity Mutual funds [Member] | Recurring [Member] |  |
Financial Assets |  |
Marketable equity securities (Registered Mutual Funds) |  | 468
International Equity Mutual funds [Member] | Recurring [Member] | Level 1 Inputs [Member] |  |
Financial Assets |  |
Marketable equity securities (Registered Mutual Funds) |  | 468
Fixed Income Mutual funds [Member] | Recurring [Member] |  |
Financial Assets |  |
Marketable equity securities (Registered Mutual Funds) |  | 3,733
Fixed Income Mutual funds [Member] | Recurring [Member] | Level 1 Inputs [Member] |  |
Financial Assets |  |
Marketable equity securities (Registered Mutual Funds) |  | $ 3,733

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