Discontinued Operations (Textual) (Details) $ in Thousands, ft² in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($) ft² property
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net gain on disposition of discontinued operations	$ 0	$ 900	$ 3,382
Discontinued Operations [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net gain on disposition of discontinued operations		900	$ 3,382
Net Rentable Space Sold | ft²			1.1
Number of properties sold (in properties) | property			14
Princeton Pike Corporate Center [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net gain on disposition of discontinued operations		$ 900