Property Dispositions - Results of Operations (Details) - Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations - USD ($) $ in Thousands		12 Months Ended
	Mar. 13, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disposal Group, Including Discontinued Operation, Income Statement Disclosures
Revenues		$ 7,245	$ 46,928	$ 47,737
Operating expenses (excluding impairment charges)		(3,150)	(25,944)	(29,365)
Impairment charges		0	(29,183)	0
Interest expense		(1,108)	(7,485)	(6,996)
Other income and (expenses)		0	0	676
Loss on extinguishment of debt		(1,364)	(15,807)	0
Equity in losses of equity method investments		(688)	(3,137)	(2,789)
Provision for income taxes		(2)	(24)	(4)
Gain on sale of real estate, net of tax	$ 1,600	2,879	132,858	2,197
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent		$ 3,812	$ 98,206	$ 11,456