Real Estate Transactions Property Transactions (Discontinued Operations) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 02, 2015 USD ($)	Jul. 15, 2015 USD ($) ft² a
Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Consideration					$ 131,000
Income (Loss) from Discontinued Operations	$ 6	$ 348	$ (14)	$ 1,806
Gain (Loss) on Disposal of Discontinued Operation	$ 0	$ 12,993	(551)	$ 19,372
Spring & 8th/ NCR [Member]
Discontinued Operations [Line Items]
Area of Land | a						4.16
Business Combination Purchase Price						$ 27,000
Net Rentable Area | ft²						485,000
2100 Ross Avenue [Member]
Discontinued Operations [Line Items]
Gain (Loss) on Disposal of Discontinued Operation			$ 36,200
Net Rentable Area | ft²						844,000