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Investments - Maturity Table (Details) - USD ($) $ in Thousands | Dec. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 2,535,568 | $ 1,986,957
Estimated Fair Value | 2,517,956 | $ 1,996,634
Maturity 2022 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 850,032 |
Estimated Fair Value | 850,326 |
Maturity 2023 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 162,617 |
Estimated Fair Value | 162,003 |
Maturity 2024 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 398,583 |
Estimated Fair Value | 394,941 |
Maturity 2026 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 547,712 |
Estimated Fair Value | 540,382 |
Maturity 2038 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 74 |
Estimated Fair Value | 79 |
Maturity 2039 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 1,029 |
Estimated Fair Value | 1,120 |
Maturity 2042 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 3,183 |
Estimated Fair Value | 3,175 |
Maturity 2043 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 5,599 |
Estimated Fair Value | 5,797 |
Maturity 2044 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 7,620 |
Estimated Fair Value | 7,881 |
Maturity 2045 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 6,764 |
Estimated Fair Value | 6,968 |
Maturity 2046 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 10,629 |
Estimated Fair Value | 10,818 |
Maturity 2047 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 12,611 |
Estimated Fair Value | 12,822 |
Maturity 2048 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 2,961 |
Estimated Fair Value | 3,025 |
Maturity 2049 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 19,828 |
Estimated Fair Value | 20,458 |
Maturity 2050 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 134,707 |
Estimated Fair Value | 131,063 |
Maturity 2051 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 178,250 |
Estimated Fair Value | 174,853 |
Maturity 2053 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 141,251 |
Estimated Fair Value | 140,260 |
Maturity 2054 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 52,118 |
Estimated Fair Value | $ 51,985 |

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