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Fair Value of Financial Instruments (Tables) | 9 Months Ended
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Sep. 30, 2012
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 September 30, 2012 and December 31, 2011.
| September 30, 2012 |  | December 31, 2011
| (Amounts in thousands)
Assets |  |  |
Investments | $ | 3,160,613 |  |  | $ | 3,062,421 |
Liabilities |  |  |
Interest rate swap agreements | $ | 260 |  |  | $ | 670 |
Equity contracts | $ | 171 |  |  | $ | 655 |
Secured notes payable | $ | 140,000 |  |  | $ | 140,000 |

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