Disclosure of Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage loans, net	$ 351,493	$ 395,202
Unsecured Debt	2,632,881	2,285,698
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage loans, net	351,493	395,202
Unsecured Debt	2,632,881	2,285,698
Long-term Debt [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage Loans | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	402,794	397,167
Long-term Debt [Member] | Fair Value, Inputs, Level 3 [Member] | Unsecured Notes | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	$ 2,795,031	$ 2,295,699