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Securities - Amortized Cost and Fair Value of Debt Securities (Details) - USD ($) $ in Thousands | Mar. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 1,057,581 | $ 1,051,313
Gross Unrealized Gains | 623 | 1,746
Gross Unrealized Losses | (88,411) | (83,751)
Fair Value | 969,793 | 969,308
Interest receivable | 3,400 | 3,800
U.S. Treasury securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 144,009 | 144,292
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (11,423) | (10,506)
Fair Value | 132,586 | 133,786
Obligations of U.S. government corporations and agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 33,302 | 33,342
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (709) | (829)
Fair Value | 32,593 | 32,513
Collateralized mortgage obligations of U.S. government corporations and agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 517,555 | 507,942
Gross Unrealized Gains | 405 | 1,068
Gross Unrealized Losses | (50,762) | (48,071)
Fair Value | 467,198 | 460,939
Residential mortgage-backed securities of U.S. government corporations and agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 43,714 | 44,707
Gross Unrealized Gains | 4 | 7
Gross Unrealized Losses | (7,056) | (6,537)
Fair Value | 36,662 | 38,177
Commercial mortgage-backed securities of U.S. government corporations and agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 293,868 | 290,775
Gross Unrealized Gains | 214 | 458
Gross Unrealized Losses | (18,333) | (17,808)
Fair Value | 275,749 | 273,425
Obligations of states and political subdivisions |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 25,133 | 30,255
Gross Unrealized Gains | 0 | 213
Gross Unrealized Losses | (128) | 0
Fair Value | $ 25,005 | $ 30,468

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