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Investment Securities - Income Earned on Securities (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Non-taxable: |  |  |  |
Total | $ 30,717 | $ 14,910 | $ 79,418 | $ 47,326
Held-to-maturity |  |  |  |
Taxable: |  |  |  |
Taxable | 1,127 | 256 | 2,477 | 715
Non-taxable: |  |  |  |
Non-taxable | 4,853 | 65 | 9,887 | 205
Available-for-sale |  |  |  |
Taxable: |  |  |  |
Taxable | 15,949 | 6,937 | 39,313 | 26,604
Non-taxable: |  |  |  |
Non-taxable | $ 8,788 | $ 7,652 | $ 27,741 | $ 19,802

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