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Financial Instruments (Tables) | 6 Months Ended
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Jun. 30, 2021
Financial Instruments, Owned, at Fair Value [Abstract] |
Estimated Fair Values of Financial Instruments | The following table presents the fair values of financial instruments:
| June 30, 2021 |  | December 31, 2020
| (Amounts in thousands)
Assets |  |  |
Investments | $ | 5,040,804 |  |  | $ | 4,729,270 |
Note receivable | 5,698 |  |  | 5,725 |
Liabilities |  |  |
Options sold | 167 |  |  | — |
Unsecured notes | 423,236 |  |  | 415,253 |

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