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Fair Value of Financial Instruments (Tables) | 6 Months Ended
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Jun. 30, 2013
Financial Instruments, Owned, at Fair Value [Abstract] |
Estimated Fair Values of Financial Instruments | The following table presents the estimated fair values of financial instruments at June 30, 2013 and December 31, 2012.
| June 30, 2013 |  | December 31, 2012
| (Amounts in thousands)
Assets |  |  |
Investments | $ | 3,176,297 |  |  | $ | 3,180,095 |
Liabilities |  |  |
Interest rate swap agreements | $ | 0 |  |  | $ | 103 |
Equity contracts | $ | 331 |  |  | $ | 175 |
Secured notes | $ | 140,000 |  |  | $ | 140,000 |

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