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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 | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2022 | Jun. 30, 2021 | Jun. 30, 2022 | Jun. 30, 2021 | Dec. 31, 2021
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Net investment income earned | $ 70,222 | $ 83,731 | $ 142,824 | $ 153,447 |
Other Investments | 429,546 |  | 429,546 |  | $ 409,032
Alternative Investments [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Net investment income earned | 9,300 | 29,900 | 28,400 | 50,100 |
Investments accounted for under the equity method [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Net investment income | 270,900 | 8,400 | 406,500 | 490,000 |
Realized gains | 6,233,500 | 1,392,500 | 8,981,500 | 2,168,600 |
Net change in unrealized appreciation | (3,962,400) | 4,948,900 | 1,215,900 | 9,579,700 |
Net income | $ 2,542,000 | $ 6,349,800 | $ 10,603,900 | $ 12,238,300 |

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