Fair Value Of Financial Instruments - Summary of Carrying Value and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Mortgages and Notes Payable | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value of long-term debt	$ 973,357	$ 854,217
Mortgages and Notes Payable | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value of long-term debt	984,420	880,866
Senior Notes and Debentures | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value of long-term debt	1,494,515	1,483,813
Senior Notes and Debentures | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value of long-term debt	$ 1,503,677	$ 1,579,868