Mortgage and Other Indebtedness - Consolidated Indebtedness by Type of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Participating Mortgage Loans [Line Items]
Principal	$ 1,298,980	$ 1,176,076
Unamortized Net Premiums	1,400	1,732
Unamortized Debt Issuance Costs	(11,386)	(7,014)
Total	1,288,994	1,170,794
Unsecured revolving credit facility
Participating Mortgage Loans [Line Items]
Principal	0	25,000
Unamortized Net Premiums	0	0
Unamortized Debt Issuance Costs	(1,253)	(1,672)
Total		23,328
Senior unsecured notes—fixed rate | Fixed rate debt
Participating Mortgage Loans [Line Items]
Principal	550,000	550,000
Unamortized Net Premiums	0	0
Unamortized Debt Issuance Costs	(3,556)	(3,595)
Total	546,444	546,405
Unsecured term loan
Participating Mortgage Loans [Line Items]
Principal	250,000	250,000
Unamortized Net Premiums	0	0
Unamortized Debt Issuance Costs	(1,488)	(1,647)
Total	248,512	248,353
Exchangeable senior notes - fixed rate | Fixed rate debt
Participating Mortgage Loans [Line Items]
Principal	175,000
Unamortized Net Premiums	0
Unamortized Debt Issuance Costs	(5,052)
Total	169,948
Mortgages notes payable | Fixed rate debt
Participating Mortgage Loans [Line Items]
Principal	294,787	295,966
Unamortized Net Premiums	1,400	1,732
Unamortized Debt Issuance Costs	(14)	(25)
Total	296,173	297,673
Mortgages notes payable | Variable rate debt
Participating Mortgage Loans [Line Items]
Principal	29,193	55,110
Unamortized Net Premiums	0	0
Unamortized Debt Issuance Costs	(23)	(75)
Total	$ 29,170	$ 55,035