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INVESTMENT AND MORTGAGE-BACKED SECURITIES - Narrative (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020
Securities available-for-sale: |  |
Acquired securities available-for-sale on the Merger Date | $ 652,000,000.0 |
Securities held-to-maturity | 177,354,000 | $ 0
Securities pledged as collateral, carrying amount | $ 726,400,000 | $ 99,400,000
Number of holdings of securities of any one issuer in an amount greater than 10% of stockholders equity | 0 | 0
Threshold for disclosure percentage | 10.00% | 10.00%
Available for sale debt securities, unrealized loss position due to credit | $ 0 |
Accrued interest receivable on securities | 4,400,000 |
Agency collateralized mortgage obligations ("CMOs") |  |
Securities available-for-sale: |  |
Securities held-to-maturity | 60,054,000 |
Pass-through mortgage-backed securities ("MBS") issued by government sponsored entities ("GSEs") |  |
Securities available-for-sale: |  |
Securities held-to-maturity | 117,300,000 |
Available for sale debt securities, unrealized loss position due to credit | $ 427,382,000 | $ 5,007,000

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