Acquisitions, Dispositions, Discontinued Operations and Assets Held for Sale Acquisitions, Dispositions, Discontinued Operations and Assets Held for Sale (Income from Discontinued Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Property revenues	$ 4,357	$ 14,219	$ 19,184	$ 28,045
Property expenses	(1,750)	(5,039)	(6,898)	(9,922)
Property revenues less property expenses	2,607	9,180	12,286	18,123
Property management expense	(66)	(151)	(242)	(321)
Depreciation and amortization	0	(3,973)	(4,327)	(7,877)
Income tax expense	(12)	0	(112)	0
Income from discontinued operations	$ 2,529	$ 5,056	$ 7,605	$ 9,925