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STOCKHOLDERS' EQUITY (Narrative) (Details) - USD ($) |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 09, 2020 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |
Preferred stock, shares authorized |  |  |  | 500,000 | 500,000 |
Shares issued and sold |  |  |  | 17,250 |  |
Preferred stock, shares outstanding |  |  |  | 17,250 | 0 |
Net proceeds from issuance of preferred stock |  |  |  | $ 166,356,000 | $ 0 | $ 0
Accounting Standards Update 2017-12 |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |
Reclassifications of unrealized gains (losses) on AFS |  | $ 400,000 |  |  |  |
Accounting Standards Update 2018-02 |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |
Amounts reclassified from AOCI into earnings |  | $ (107,000) |  |  |  |
Accounting Standards Update 2016-01 |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |
Amounts reclassified from AOCI into earnings |  |  | $ (61,000) |  |  |
Depositary Shares |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |
Shares issued and sold | 6,900,000 |  |  |  |  |
Number of shares to be purchased upon the exercise of options | 900,000 |  |  |  |  |
Preferred stock, liquidation preference (usd per share) | $ 25 |  |  |  |  |
Series A Preferred Stock |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |
Number of preferred stock represented by each depositary share | The Series A preferred stock is represented by depositary shares, each representing a 1/400th ownership interest in a share of Series A preferred stock |  |  |  |  |
Preferred stock, liquidation preference (usd per share) | $ 10,000 |  |  |  |  |
Net proceeds from issuance of preferred stock | $ 166,400,000 |  |  |  |  |

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