Disclosure of Fair Value of Financial Instruments (Details) (Fair Value, Inputs, Level 3 [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Carrying Value | Mortgage Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 534,547	$ 545,306
Carrying Value | Unsecured Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	2,508,886	2,708,213
Fair Value | Mortgage Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	550,722	573,944
Fair Value | Unsecured Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 2,634,931	$ 2,764,831