Fair Value of Financial Instruments - Summary of Carrying Value and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Mortgages payable and notes payable | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value of long-term debt	$ 813,958	$ 750,268
Mortgages payable and notes payable | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value of long-term debt	826,012	760,260
Senior notes and debentures | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value of long-term debt	2,377,939	1,976,594
Senior notes and debentures | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value of long-term debt	$ 2,452,494	$ 2,015,973