Discontinued Operations (Textual) (Details) $ in Thousands, ft² in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 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	$ 0	$ 900
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
Net Rentable Space Sold | ft²			1.1
Number of properties sold post closing activity (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