Schedule III - Real Estate and Accumulated Depreciation - Reconciliation of Gross Real Estate Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]
Balance, beginning of year	$ 12,939,229	$ 13,592,440	$ 13,577,700
Additions:
Acquisitions	275,581	351,135	437,227
Improvements	31,314	56,446	31,898
Deductions/Other:
Dispositions	(340,290)	(947,403)	(368,808)
Impairments	(102,941)	(81,078)	(84,278)
Reclassification to assets held for sale	(71,481)	(33,724)	(2,997)
Other	(247)	1,413	1,698
Balance, end of year	$ 12,731,165	$ 12,939,229	$ 13,592,440