Schedule III - Real Estate and Accumulated Depreciation - Changes in Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Accumulated Depreciation [Roll Forward]
Balance, beginning of year	$ 2,217,108	$ 1,766,006	$ 1,331,751
Additions:
Depreciation expense	497,511	548,901	586,321
Deductions:
Dispositions	(57,346)	(34,086)	(77,987)
Impairments	(32,147)	(50,828)	(69,040)
Reclassified to assets held for sale	(400)	(12,885)	(5,039)
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Accumulated Depreciation, Other Deduction	(1,847)	0	0
Balance, end of year	$ 2,622,879	$ 2,217,108	$ 1,766,006