Rental Income and Future Minimum Rent - Rental income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Fixed lease payments	$ 201,324	$ 197,295	$ 603,386	$ 585,257
Variable lease payments	31,479	31,650	89,293	93,059
Net collectability reversals	(2,083)	(1,823)	(2,830)	(14,205)
Total rental income	230,720	227,122	689,849	664,111
Reduction of revenue primarily as a result of the COVID-19 pandemic		$ (1,800)		$ (14,200)
Excluded rent revenue recognized in association with tenants restored to accrual basis	$ 700		$ 700