Disclosure of Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage loans, net	$ 297,326	$ 395,202
Unsecured Debt	2,633,941	2,285,698
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage loans, net	297,326	395,202
Unsecured Debt	2,633,941	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	304,689	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	$ 2,821,931	$ 2,295,699