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INVESTMENT AND MORTGAGE-BACKED SECURITIES - Sales Information and Marketable Equity Securities (Details) - USD ($) | 3 Months Ended | 9 Months Ended | 15 Months Ended
--- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021
Sales of Available-for-sale Securities: |  |  |  |  |
Proceeds |  |  | $ 138,077,000 | $ 68,784,000 |
Proceeds: |  |  |  |  |
Marketable equity securities |  | $ 137,000 | 6,101,000 | 410,000 |
Net gain on equity securities | $ 0 | 175,000 | 131,000 | 139,000 |
Sales of securities held-to-maturity |  |  | 0 | 0 | $ 0
Transfers to or from securities held-to-maturity | $ 0 | 0 | 0 | 0 |
Agency Notes |  |  |  |  |
Sales of Available-for-sale Securities: |  |  |  |  |
Proceeds |  |  |  | 273,000 |
Corporate Securities |  |  |  |  |
Sales of Available-for-sale Securities: |  |  |  |  |
Proceeds |  |  | 50,273,000 | 25,403,000 |
Gross gains |  |  | 729,000 | 1,344,000 |
Tax expense on gain |  |  | 232,000 | 423,000 |
Gross losses |  |  | 41,000 |  |
Tax benefit on loss |  |  | 13,000 |  |
Pass-through MBS issued by GSEs |  |  |  |  |
Sales of Available-for-sale Securities: |  |  |  |  |
Proceeds |  | 5,987,000 | 26,823,000 | 39,182,000 |
Gross gains |  | 215,000 | 187,000 | 2,005,000 |
Tax expense on gain |  | $ 67,000 | 59,000 | 630,000 |
Gross losses |  |  | 35,000 |  |
Tax benefit on loss |  |  | 11,000 |  |
Agency Collateralized Mortgage Obligations ("CMOs") |  |  |  |  |
Sales of Available-for-sale Securities: |  |  |  |  |
Proceeds |  |  | 41,324,000 | 4,199,000 |
Gross gains |  |  | 268,000 | 8,000 |
Tax expense on gain |  |  | 85,000 | $ 3,000 |
Gross losses |  |  | 44,000 |  |
Tax benefit on loss |  |  | 14,000 |  |
State and municipal obligations. |  |  |  |  |
Sales of Available-for-sale Securities: |  |  |  |  |
Proceeds |  |  | 19,657,000 |  |
Gross gains |  |  | 143,000 |  |
Tax expense on gain |  |  | $ 45,000 |  |

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