Supplemental Cash Flow Disclosures (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Supplemental disclosures:
Cash paid for interest	$ 204,366	$ 200,617
Cash paid for income taxes	5,346	10,690
Non-cash investing and financing activities:
Accrued capital expenditures, tenant improvements and real estate developments	5,762	6,750
Accrued deferred financing costs	169	181
Distributions declared and unpaid	145,673	146,596
Mortgage note payable relieved by foreclosure or a deed-in-lieu of foreclosure	16,200	100,388
Mortgage notes payable assumed in real estate disposition	0	66,000
Real estate investments received from a ground lease expiration and other lease related transactions	1,386	259
Nonmonetary exchanges:
Real estate investments received	0	50,204
Real estate investments relinquished and gain on disposition	0	(47,474)
Rent and tenant receivables, intangible lease liability and other assets, net	$ 0	$ (2,511)