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Securities - Fair Values and Amortized Costs Securities (Details) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 790,208 | $ 737,005
Gross Unrealized Gains | 26,563 | 33,478
Gross Unrealized Losses | (2,888) | (90)
Fair Value | 813,883 | 770,393
Marketable equity securities | 3,416 | 3,300
Total Securities | 817,299 | 773,693
Interest receivable | 3,200 | 3,400
U.S. Treasury securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 63,361 | 9,980
Gross Unrealized Gains | 259 | 302
Gross Unrealized Losses | (352) | 0
Fair Value | 63,268 | 10,282
Obligations of U.S. government corporations and agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 78,715 | 78,755
Gross Unrealized Gains | 3,313 | 4,149
Gross Unrealized Losses | 0 | 0
Fair Value | 82,028 | 82,904
Collateralized mortgage obligations of U.S. government corporations and agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 213,394 | 202,975
Gross Unrealized Gains | 5,716 | 6,410
Gross Unrealized Losses | (1,194) | (89)
Fair Value | 217,916 | 209,296
Residential mortgage-backed securities of U.S. government corporations and agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 64,496 | 66,960
Gross Unrealized Gains | 632 | 818
Gross Unrealized Losses | (1,217) | 0
Fair Value | 63,911 | 67,778
Commercial mortgage-backed securities of U.S. government corporations and agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 266,292 | 258,875
Gross Unrealized Gains | 11,085 | 14,806
Gross Unrealized Losses | (124) | 0
Fair Value | 277,253 | 273,681
Corporate obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 2,001 | 2,021
Gross Unrealized Gains | 2 | 5
Gross Unrealized Losses | (1) | (1)
Fair Value | 2,002 | 2,025
Obligations of states and political subdivisions |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 101,949 | 117,439
Gross Unrealized Gains | 5,556 | 6,988
Gross Unrealized Losses | 0 | 0
Fair Value | $ 107,505 | $ 124,427

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