Property Transactions (Gain (Loss) on Sales of Discontinued Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Document Fiscal Year Focus	2015	2014	2013
Gain on sale of investment properties included in discontinued operations
Gain (loss) on sale from discontinued operations	$ (551)	$ 19,358	$ 11,489