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Investments - Narrative (Details) - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Investment Holdings [Line Items] |  |
Investment grade rating | 93.90% |
Limited partnership interests | $ 383,717 | $ 328,516
Fair value of issued securities | 5,791,676 | 7,515,318
FHLB funding agreements | 545,000 | 675,000
Governmental agencies as required by law in various states |  |
Investment Holdings [Line Items] |  |
Fair value of issued securities | 26,000 | 17,700
FHLB of Chicago |  |
Investment Holdings [Line Items] |  |
Fair value of issued securities | $ 594,200 | $ 740,000

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