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Fair Value of Financial Instruments (Tables) | 12 Months Ended
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Dec. 31, 2016
Financial Instruments, Owned, at Fair Value [Abstract] |
Estimated Fair Values of Financial Instruments | The following table presents estimated fair values of financial instruments:
| December 31,
| 2016 |  | 2015
| (Amounts in thousands)
Assets |  |  |
Investments | $ | 3,547,560 |  |  | $ | 3,380,642 |
Total return swaps | 667 |  |  | — |
Liabilities |  |  |
Total return swaps | $ | 765 |  |  | $ | 11,525 |
Options sold | 20 |  |  | 260 |
Secured notes | 140,000 |  |  | 140,000 |
Unsecured note | 180,000 |  |  | 150,000 |

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