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Disclosure of Fair Value of Financial Instruments (Details) (Fair Value, Inputs, Level 3 [Member], USD $)
In Thousands, unless otherwise specified |
Mar. 31, 2015
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Dec. 31, 2014
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|---|---|---|
| Estimate of Fair Value Measurement [Member] | Mortgage Loans | ||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
| Long-term Debt, Fair Value | $ 496,873 | $ 501,231 |
| Estimate of Fair Value Measurement [Member] | Unsecured Notes | ||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
| Long-term Debt, Fair Value | 2,769,146 | 2,704,069 |
| Portion at Other than Fair Value Measurement [Member] | Mortgage Loans | ||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
| Long-term Debt, Fair Value | 484,584 | 487,301 |
| Portion at Other than Fair Value Measurement [Member] | Unsecured Notes | ||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
| Long-term Debt, Fair Value | $ 2,607,874 | $ 2,509,094 |