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Investments - Maturity Table (Details) - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 485,756 | $ 182,325
Estimated Fair Value | 487,669 | $ 176,245
Maturity 2020 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 77,240 |
Estimated Fair Value | 77,385 |
Maturity 2021 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 138,157 |
Estimated Fair Value | 138,640 |
Maturity 2022 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 34,997 |
Estimated Fair Value | 34,983 |
Maturity 2038 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 176 |
Estimated Fair Value | 191 |
Maturity 2039 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 2,597 |
Estimated Fair Value | 2,778 |
Maturity 2042 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 7,196 |
Estimated Fair Value | 7,050 |
Maturity 2043 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 11,661 |
Estimated Fair Value | 11,813 |
Maturity 2044 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 17,300 |
Estimated Fair Value | 17,487 |
Maturity 2045 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 18,280 |
Estimated Fair Value | 18,332 |
Maturity 2046 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 28,892 |
Estimated Fair Value | 28,822 |
Maturity 2047 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 45,411 |
Estimated Fair Value | 45,353 |
Maturity 2048 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 12,154 |
Estimated Fair Value | 12,478 |
Maturity 2049 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 91,695 |
Estimated Fair Value | $ 92,357 |

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