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Investments - Maturity Table (Details) - USD ($) $ in Thousands | Mar. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 607,867 | $ 485,756
Estimated Fair Value | 614,582 | $ 487,669
2020 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 94,048 |
Estimated Fair Value | 94,320 |
2021 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 145,340 |
Estimated Fair Value | 147,711 |
2022 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 54,127 |
Estimated Fair Value | 54,317 |
2023 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 12,977 |
Estimated Fair Value | 13,341 |
2038 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 175 |
Estimated Fair Value | 192 |
2039 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 2,457 |
Estimated Fair Value | 2,668 |
2042 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 7,115 |
Estimated Fair Value | 7,172 |
2043 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 11,130 |
Estimated Fair Value | 11,560 |
2044 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 16,149 |
Estimated Fair Value | 16,684 |
2045 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 16,896 |
Estimated Fair Value | 17,286 |
2046 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 27,641 |
Estimated Fair Value | 28,385 |
2047 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 39,927 |
Estimated Fair Value | 40,313 |
2048 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 10,248 |
Estimated Fair Value | 10,664 |
2049 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 84,282 |
Estimated Fair Value | 87,458 |
2050 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 6,550 |
Estimated Fair Value | 6,671 |
2054 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 78,805 |
Estimated Fair Value | $ 75,840 |

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