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Financial Instruments (Tables) | 6 Months Ended
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Jun. 30, 2018
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, 2018 |  | December 31, 2017
| (Amounts in thousands)
Assets |  |  |
Investments | $ | 3,834,156 |  |  | $ | 3,732,728 |
Note receivable | 5,516 |  |  | 5,565 |
Liabilities |  |  |
Total return swap | $ | 1,393 |  |  | $ | 1,200 |
Options sold | 780 |  |  | 123 |
Unsecured notes | 364,736 |  |  | 385,583 |

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