Schedule III - Real Estate and Accumulated Depreciation - Changes in Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance, beginning of year	$ 1,766,006	$ 1,331,751	$ 775,050
Additions:
Depreciation expense	548,901	586,321	630,347
Deductions:
Dispositions	(34,086)	(77,987)	(49,907)
Impairments	(50,828)	(69,040)	(23,196)
Reclassified to assets held for sale	(12,885)	(5,039)	(543)
Balance, end of year	$ 2,217,108	$ 1,766,006	$ 1,331,751