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Investments (Aggregated Income Statement Summarized Financial Information for Partnerhips in our Alternative Investment Portfolio) (Details) - USD ($) $ in Thousands | 3 Months Ended |
--- | --- | ---
Mar. 31, 2022 | Mar. 31, 2021 | Dec. 31, 2021
Schedule of Equity Method Investments [Line Items] |  |  |
Net investment income earned | $ 72,602 | $ 69,716 |
Carrying Value | 425,666 |  | $ 409,032
Alternative Investments [Member] |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Net investment income earned | 19,100 | 20,200 |
Investments accounted for under the equity method [Member] |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Net investment income | 135,500 | 481,600 |
Realized gains | 2,748,000 | 776,000 |
Net change in unrealized appreciation | 5,178,200 | 4,630,800 |
Insurance Subsidiaries' alternative investments income | $ 8,061,700 | $ 5,888,400 |

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