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Investment Information - Other investments (Details) - USD ($) $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
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Schedule Of Other Investments [Line Items] |  |  |
Other investments measured at fair value |  | $ 2,043,970 | $ 3,824,796
Other investable assets | [1] | 0 | 500,000
Other investments (portion measured at fair value: $2,043,970 and $3,824,796) |  | 2,043,970 | 4,324,796
Fair value option | Fixed maturities |  |  |
Schedule Of Other Investments [Line Items] |  |  |
Other investments measured at fair value |  | 414,007 | 843,354
Fair value option | Other investments |  |  |
Schedule Of Other Investments [Line Items] |  |  |
Other investments measured at fair value |  | 1,489,759 | 2,331,885
Fair value option | Other investments | Term loan investments |  |  |
Schedule Of Other Investments [Line Items] |  |  |
Other investments measured at fair value |  | 528,585 | 1,231,731
Fair value option | Other investments | Lending |  |  |
Schedule Of Other Investments [Line Items] |  |  |
Other investments measured at fair value |  | 579,563 | 572,636
Fair value option | Other investments | Credit related funds |  |  |
Schedule Of Other Investments [Line Items] |  |  |
Other investments measured at fair value |  | 56,997 | 90,780
Fair value option | Other investments | Energy |  |  |
Schedule Of Other Investments [Line Items] |  |  |
Other investments measured at fair value |  | 84,880 | 65,813
Fair value option | Other investments | Investment grade fixed income |  |  |
Schedule Of Other Investments [Line Items] |  |  |
Other investments measured at fair value |  | 131,910 | 138,646
Fair value option | Other investments | Infrastructure |  |  |
Schedule Of Other Investments [Line Items] |  |  |
Other investments measured at fair value |  | 26,359 | 165,516
Fair value option | Other investments | Private equity |  |  |
Schedule Of Other Investments [Line Items] |  |  |
Other investments measured at fair value |  | 81,465 | 48,750
Fair value option | Other investments | Real estate |  |  |
Schedule Of Other Investments [Line Items] |  |  |
Other investments measured at fair value |  | 0 | 18,013
Fair value option | Short-term investments |  |  |
Schedule Of Other Investments [Line Items] |  |  |
Other investments measured at fair value |  | 115,681 | 557,008
Fair value option | Equity securities |  |  |
Schedule Of Other Investments [Line Items] |  |  |
Other investments measured at fair value |  | $ 24,523 | $ 92,549
[1] | Participation interests in a receivable of a reverse repurchase agreement

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