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
	Mar. 31, 2016	Mar. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Property revenues	$ 14,827	$ 13,826
Property expenses	(5,148)	(4,883)
Property revenues less property expenses	9,679	8,943
Property management expense	(176)	(170)
Depreciation and amortization	(4,327)	(3,904)
Income tax expense	(100)	0
Income from discontinued operations	$ 5,076	$ 4,869