Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Total revenues	$ 1,161,366	$ 1,238,054	$ 1,258,028
COVID-19 [Member]
Segment Reporting Information [Line Items]
Deferral agreements	17,900
Rental Revenue [Member]
Segment Reporting Information [Line Items]
Reduction of revenue	37,000
General reserve increase	10,200
Not probable for collection	20,700
Straight line rent receivable, receivable	6,200
COVID-19 effect	26,500
COVID-19 effect, general reserve increase	9,600
COVID-19 effect, amount not probable for collection	13,400
COVID-19 effect, straight line rent receivable, increase in reserve	3,500
Total revenues	1,158,285	1,237,234	1,257,867
Rental Revenue [Member] | COVID-19 [Member]
Segment Reporting Information [Line Items]
Deferral agreements, abated	18,300
Fees From Managed Partnership [Member]
Segment Reporting Information [Line Items]
Total revenues	$ 3,081	$ 820	$ 161