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Investments - Maturities of Fixed Maturities (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017
Amortized Cost |  |
Due in 1 year or less | $ 358,797 |
Due after 1 year through 5 years | 1,690,400 |
Due after 5 years through 10 years | 2,453,572 |
Due after 10 years through 20 years | 1,931,599 |
Due after 20 years | 939,543 |
Amortized Cost/Cost | 7,373,911 | $ 7,302,950
Fair Value |  |
Due in 1 year or less | 363,049 |
Due after 1 year through 5 years | 1,713,593 |
Due after 5 years through 10 years | 2,465,337 |
Due after 10 years through 20 years | 1,991,726 |
Due after 20 years | 981,613 |
Total | $ 7,515,318 | $ 7,724,075
Percent of Total Fair Value |  |
Due in 1 year or less | 4.80% |
Due after 1 year through 5 years | 22.80% |
Due after 5 years through 10 years | 32.80% |
Due after 10 years through 20 years | 26.50% |
Due after 20 years | 13.10% |
Total | 100.00% |
Average option-adjusted duration, in years | 5 years 10 months 24 days |

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