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Financial Instruments (Tables) | 12 Months Ended
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Dec. 31, 2019
Financial Instruments, Owned, at Fair Value [Abstract] |
Estimated Fair Values of Financial Instruments | The following table presents the fair values of financial instruments:
| December 31,
| 2019 |  | 2018
| (Amounts in thousands)
Assets |  |  |
Investments | $ | 4,312,161 |  |  | $ | 3,768,091 |
Note receivable | 5,665 |  |  | 5,557 |
Liabilities |  |  |
Total return swaps | — |  |  | 4,851 |
Options sold | 77 |  |  | 3 |
Unsecured notes | 394,279 |  |  | 362,674 |

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