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Securities - Fair Values and Amortized Costs Securities (Details) - USD ($) $ in Thousands | Jun. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 815,280 | $ 737,005
Gross Unrealized Gains | 25,494 | 33,478
Gross Unrealized Losses | (1,495) | (90)
Fair Value | 839,279 | 770,393
Marketable equity securities | 1,096 | 3,300
Total Securities | 840,375 | 773,693
Interest receivable | 3,200 | 3,100
U.S. Treasury securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 74,253 | 9,980
Gross Unrealized Gains | 551 | 302
Gross Unrealized Losses | 0 | 0
Fair Value | 74,804 | 10,282
Obligations of U.S. government corporations and agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 78,674 | 78,755
Gross Unrealized Gains | 2,950 | 4,149
Gross Unrealized Losses | 0 | 0
Fair Value | 81,624 | 82,904
Collateralized mortgage obligations of U.S. government corporations and agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 197,458 | 202,975
Gross Unrealized Gains | 4,762 | 6,410
Gross Unrealized Losses | (870) | (89)
Fair Value | 201,350 | 209,296
Residential mortgage-backed securities of U.S. government corporations and agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 63,896 | 66,960
Gross Unrealized Gains | 548 | 818
Gross Unrealized Losses | (585) | 0
Fair Value | 63,859 | 67,778
Commercial mortgage-backed securities of U.S. government corporations and agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 314,228 | 258,875
Gross Unrealized Gains | 11,114 | 14,806
Gross Unrealized Losses | (39) | 0
Fair Value | 325,303 | 273,681
Corporate obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 500 | 2,021
Gross Unrealized Gains | 0 | 5
Gross Unrealized Losses | (1) | (1)
Fair Value | 499 | 2,025
Obligations of states and political subdivisions |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 86,271 | 117,439
Gross Unrealized Gains | 5,569 | 6,988
Gross Unrealized Losses | 0 | 0
Fair Value | $ 91,840 | $ 124,427

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