Leases - Rental Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Cash rent	$ 1,036,422	$ 1,102,538	$ 1,121,482
Straight-line rent	25,161	28,032	39,772
Lease intangible amortization	(3,357)	(2,538)	(4,178)
Property operating cost reimbursements	5,866	5,559	5,375
Sub-lease	20,141	21,496	16,178
Total fixed	1,084,233	1,155,087	1,178,629
Variable	73,404	81,310	78,179
Income from direct financing leases	648	837	1,059
Total rental revenue	1,158,285	$ 1,237,234	$ 1,257,867
COVID-19 [Member]
Lessor, Lease, Description [Line Items]
Deferral agreements	17,900
Rental Revenue [Member]
Lessor, Lease, Description [Line Items]
COVID-19 effect, excluding straight line rent reserve	23,000
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
Rental Revenue [Member] | COVID-19 [Member]
Lessor, Lease, Description [Line Items]
Deferral agreements, abated	$ 18,300