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Investment Securities - Amortized Cost to Approximate Fair Value (Details) - USD ($) $ in Thousands | Mar. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Available for sale securities: |  |
Amortized Cost | $ 1,062,830 | $ 1,116,954
Gross Unrealized Gains | 15 | 50
Gross Unrealized Losses | 1,557 | 3,317
Fair Value | 1,061,288 | 1,113,687
Accrued interest on securities available for sale | 5,100 | 6,700
Held to maturity securities: |  |
Amortized Cost | 1,175,167 | 1,204,217
Gross Unrealized Gains | 2,385 | 973
Gross Unrealized Losses | 1,374 | 1,655
Fair Value | 1,176,178 | 1,203,535
Accrued interest on securities held to maturity | 5,600 | 5,800
Treasury notes |  |
Available for sale securities: |  |
Amortized Cost | 109,146 | 129,261
Gross Unrealized Gains | 15 | 45
Gross Unrealized Losses | 58 | 338
Fair Value | 109,103 | 128,968
Federal agencies |  |
Available for sale securities: |  |
Amortized Cost | 240,000 | 250,731
Gross Unrealized Losses | 1,499 | 2,976
Fair Value | 238,501 | 247,755
Mortgage-backed - Agency |  |
Held to maturity securities: |  |
Amortized Cost | 11,976 | 12,016
Gross Unrealized Losses | 868 | 822
Fair Value | 11,108 | 11,194
Mortgage-backed - Government Agency ("Agency") |  |
Available for sale securities: |  |
Amortized Cost | 13,044 | 14,465
Gross Unrealized Gains |  | 5
Gross Unrealized Losses |  | 3
Fair Value | 13,044 | 14,467
Mortgage-backed - Agency - fair value option |  |
Available for sale securities: |  |
Amortized Cost | 228,448 | 236,997
Fair Value | 228,448 | 236,997
Mortgage-backed - Non-Agency multi-family |  |
Held to maturity securities: |  |
Amortized Cost | 710,024 | 719,662
Gross Unrealized Losses | 419 | 415
Fair Value | 709,605 | 719,247
Mortgage-backed - Non-Agency residential |  |
Available for sale securities: |  |
Amortized Cost | 472,192 | 485,500
Fair Value | 472,192 | 485,500
Held to maturity securities: |  |
Amortized Cost | 453,167 | 472,539
Gross Unrealized Gains | 2,385 | 973
Gross Unrealized Losses | 87 | 418
Fair Value | $ 455,465 | $ 473,094

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