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SECURITIES (Tables) | 3 Months Ended
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Mar. 31, 2024
SECURITIES |
Schedule of major categories of securities owned by entity | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | March 31, 2024
​ | ​ | ​ | ​ | ​ | Gross | ​ | Gross | ​ | ​ | ​
​ | ​ | Amortized | ​ | Unrealized | ​ | Unrealized | ​ | Fair
(In thousands) |  | Cost |  | Gains |  | Losses |  | Value
Securities available-for-sale: |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |
Agency notes | ​ | $ | 10,000 | ​ | $ | — | ​ | $ | (591) | ​ | $ | 9,409
Treasury securities | ​ | ​ | 238,622 | ​ | ​ | — | ​ | ​ | (10,451) | ​ | ​ | 228,171
Corporate securities | ​ |  | 169,954 | ​ |  | 255 | ​ |  | (19,964) | ​ |  | 150,245
Pass-through mortgage-backed securities ("MBS") issued by government sponsored entities ("GSEs") | ​ |  | 221,666 | ​ |  | 16 | ​ |  | (25,806) | ​ |  | 195,876
Agency CMOs | ​ |  | 297,445 | ​ |  | 20 | ​ |  | (47,625) | ​ |  | 249,840
State and municipal obligations | ​ | ​ | 27,654 | ​ | ​ | — | ​ | ​ | (1,979) | ​ | ​ | 25,675
Total securities available-for-sale | ​ | $ | 965,341 | ​ | $ | 291 | ​ | $ | (106,416) | ​ | $ | 859,216
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | March 31, 2024
​ | ​ | ​ | ​ | ​ | Gross | ​ | Gross | ​ | ​ | ​
​ | ​ | Amortized | ​ | Unrecognized | ​ | Unrecognized | ​ | Fair
(In thousands) |  | Cost |  | Gains |  | Losses |  | Value
Securities held-to-maturity: |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |
Agency notes | ​ | $ | 89,666 | ​ | $ | — | ​ | $ | (11,891) | ​ | $ | 77,775
Corporate securities | ​ | ​ | 9,000 | ​ | ​ | — | ​ | ​ | (1,530) | ​ | ​ | 7,470
Pass-through MBS issued by GSEs | ​ | ​ | 275,907 | ​ | ​ | — | ​ | ​ | (41,743) | ​ | ​ | 234,164
Agency CMOs | ​ |  | 214,758 | ​ |  | — | ​ |  | (29,449) | ​ |  | 185,309
Total securities held-to-maturity | ​ | $ | 589,331 | ​ | $ | — | ​ | $ | (84,613) | ​ | $ | 504,718
​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, 2023
​ | ​ | ​ | ​ | ​ | Gross | ​ | Gross | ​ | ​ | ​
​ | ​ | Amortized | ​ | Unrealized | ​ | Unrealized | ​ | Fair
(In thousands) |  | Cost |  | Gains |  | Losses |  | Value
Securities available-for-sale: |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |
Agency notes | ​ | $ | 10,000 | ​ | $ | — | ​ | $ | (629) | ​ | $ | 9,371
Treasury securities | ​ | ​ | 245,877 | ​ | ​ | — | ​ | ​ | (11,687) | ​ | ​ | 234,190
Corporate securities | ​ | ​ | 174,978 | ​ |  | — | ​ |  | (23,808) | ​ |  | 151,170
Pass-through MBS issued by GSEs | ​ |  | 230,253 | ​ |  | 10 | ​ |  | (24,978) | ​ |  | 205,285
Agency CMOs | ​ |  | 305,860 | ​ |  | 46 | ​ |  | (46,491) | ​ |  | 259,415
State and municipal obligations | ​ |  | 28,741 | ​ | ​ | — | ​ | ​ | (1,932) | ​ | ​ | 26,809
Total securities available-for-sale | ​ | $ | 995,709 | ​ | $ | 56 | ​ | $ | (109,525) | ​ | $ | 886,240
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, 2023
​ | ​ | ​ | ​ | ​ | Gross | ​ | Gross | ​ | ​ | ​
​ | ​ | Amortized | ​ | Unrecognized | ​ | Unrecognized | ​ | Fair
(In thousands) |  | Cost |  | Gains |  | Losses |  | Value
Securities held-to-maturity: |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |
Agency notes | ​ | $ | 89,563 | ​ | $ | — | ​ | $ | (11,300) | ​ | $ | 78,263
Corporate securities | ​ | ​ | 9,000 | ​ | ​ | — | ​ | ​ | (1,825) | ​ | ​ | 7,175
Pass-through MBS issued by GSEs | ​ | ​ | 279,853 | ​ | ​ | — | ​ | ​ | (37,579) | ​ | ​ | 242,274
Agency CMOs | ​ |  | 216,223 | ​ |  | 16 | ​ |  | (27,021) | ​ |  | 189,218
Total securities held-to-maturity | ​ | $ | 594,639 | ​ | $ | 16 | ​ | $ | (77,725) | ​ | $ | 516,930
Schedule of amortized cost and fair value of debt securities | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | March 31, 2024
​ | ​ | Amortized | ​ | Fair
(In thousands) | ​ | Cost | ​ | Value
Available-for-sale | ​ | ​ | ​ | ​ | ​ | ​
Within one year | ​ | $ | 124,638 | ​ | $ | 121,393
One to five years | ​ | ​ | 164,579 | ​ | ​ | 153,104
Five to ten years | ​ | ​ | 157,013 | ​ | ​ | 139,003
Beyond ten years | ​ | ​ | — | ​ | ​ | —
Pass-through MBS issued by GSEs and agency CMOs | ​ | ​ | 519,111 | ​ | ​ | 445,716
Total | ​ | $ | 965,341 | ​ | $ | 859,216
​ | ​ | ​ | ​ | ​ | ​ | ​
Held-to-maturity | ​ | ​ | ​ | ​ | ​ | ​
Within one year | ​ | $ | — | ​ | $ | —
One to five years | ​ | ​ | 19,795 | ​ | ​ | 18,292
Five to ten years | ​ | ​ | 78,871 | ​ | ​ | 66,953
Beyond ten years | ​ | ​ | — | ​ | ​ | —
Pass-through MBS issued by GSEs and agency CMOs | ​ | ​ | 490,665 | ​ | ​ | 419,473
Total | ​ | $ | 589,331 | ​ | $ | 504,718
Summary of sale of available-for-sale securities | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three Months Ended
​ | ​ | March 31,
(In thousands) |  | 2024 |  | 2023
Securities available-for-sale | ​ | ​ | ​ | ​ | ​ | ​
Proceeds | ​ | $ | — | ​ | $ | 77,804
Gross gains | ​ | ​ | — | ​ | ​ | 130
Tax expense on gains | ​ | ​ | — | ​ | ​ | 39
Gross losses | ​ | ​ | — | ​ | ​ | 1,577
Tax benefit on losses | ​ | ​ | — | ​ | ​ | 467
Schedule of gross unrealized losses and fair value of investment securities | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | March 31, 2024
​ | ​ | Less than 12 | ​ | 12 Consecutive | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Consecutive Months | ​ | Months or Longer | ​ | Total
​ | ​ | Fair | ​ | Unrealized | ​ | Fair | ​ | Unrealized | ​ | Fair | ​ | Unrealized
(In thousands) |  | Value |  | Losses |  | Value |  | Losses |  | Value |  | Losses
Securities available-for-sale: |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |
Agency notes | ​ | $ | — | ​ | $ | — | ​ | $ | 9,409 | ​ | $ | 591 | ​ | $ | 9,409 | ​ | $ | 591
Treasury securities | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 228,171 | ​ | ​ | 10,451 | ​ | ​ | 228,171 | ​ | ​ | 10,451
Corporate securities | ​ | ​ | 6,337 | ​ | ​ | 500 | ​ | ​ | 128,603 | ​ | ​ | 19,464 | ​ | ​ | 134,940 | ​ | ​ | 19,964
Pass-through MBS issued by GSEs | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 194,066 | ​ | ​ | 25,806 | ​ | ​ | 194,066 | ​ | ​ | 25,806
Agency CMOs | ​ | ​ | 2,459 | ​ | ​ | 11 | ​ | ​ | 242,361 | ​ | ​ | 47,614 | ​ | ​ | 244,820 | ​ | ​ | 47,625
State and municipal obligations | ​ |  | 3,489 | ​ |  | 11 | ​ |  | 22,186 | ​ |  | 1,968 | ​ | ​ | 25,675 | ​ | ​ | 1,979
​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, 2023
​ | ​ | Less than 12 | ​ | 12 Consecutive | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Consecutive Months | ​ | Months or Longer | ​ | Total
​ | ​ | Fair | ​ | Unrealized | ​ | Fair | ​ | Unrealized | ​ | Fair | ​ | Unrealized
(In thousands) |  | Value |  | Losses |  | Value |  | Losses |  | Value |  | Losses
Securities available-for-sale: |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |
Agency Notes | ​ | $ | — | ​ | $ | — | ​ | $ | 9,371 | ​ | $ | 629 | ​ | $ | 9,371 | ​ | $ | 629
Treasury securities | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 234,190 | ​ | ​ | 11,687 | ​ | ​ | 234,190 | ​ | ​ | 11,687
Corporate securities | ​ | ​ | 20,935 | ​ | ​ | 917 | ​ | ​ | 130,235 | ​ | ​ | 22,891 | ​ | ​ | 151,170 | ​ | ​ | 23,808
Pass-through MBS issued by GSEs | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 203,469 | ​ | ​ | 24,978 | ​ | ​ | 203,469 | ​ | ​ | 24,978
Agency CMOs | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 251,900 | ​ | ​ | 46,491 | ​ | ​ | 251,900 | ​ | ​ | 46,491
State and municipal obligations | ​ | ​ | 1,796 | ​ |  | 54 | ​ |  | 21,513 | ​ |  | 1,878 | ​ | ​ | 23,309 | ​ | ​ | 1,932
​

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