Supplemental Cash Flow Disclosures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental disclosures:
Cash paid for interest	$ 267,400	$ 260,951	$ 317,170
Cash paid for income taxes	5,589	11,280	20,279
Cash received from federal income tax refund	2,939	16,686	0
Non-cash investing and financing activities:
Accrued capital expenditures, tenant improvements and real estate developments	12,648	6,578	7,701
Accrued deferred financing costs	67	0	3
Distributions declared and unpaid	148,383	149,768	149,281
Accrued equity issuance costs	0	0	9
Mortgage note payable relieved by foreclosure or a deed-in-lieu of foreclosure	16,200	100,388	38,050
Mortgage notes payable assumed in real estate disposition	0	66,000	55,000
Real estate investments received from a ground lease expiration and other lease related transactions	1,386	259	0
Real estate investments received from a property-related legal settlement	0	775	0
Nonmonetary exchanges:
Real estate investments received	0	50,204	0
Real estate investments relinquished and gain on disposition	0	(47,474)	0
Rent and tenant receivables, intangible lease liability and other assets, net	$ 0	$ (2,511)	$ 0