Real Estate - Discontinued Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012 sqft	Jun. 30, 2013 1700 Research Boulevard [Member]	Jun. 30, 2012 1700 Research Boulevard [Member]	Jun. 30, 2013 1700 Research Boulevard [Member]	Jun. 30, 2012 1700 Research Boulevard [Member]	Dec. 31, 2012 1700 Research Boulevard [Member] sqft	Jun. 30, 2013 Atrium Building [Member]	Jun. 30, 2012 Atrium Building [Member]	Jun. 30, 2013 Atrium Building [Member]	Jun. 30, 2012 Atrium Building [Member]	Mar. 19, 2013 Atrium Building [Member] sqft	Jun. 30, 2013 Plumtree Medical Center [Member]	Jun. 30, 2012 Plumtree Medical Center [Member]	Jun. 30, 2013 Plumtree Medical Center [Member]	Jun. 30, 2012 Plumtree Medical Center [Member]	Dec. 31, 2012 Plumtree Medical Center [Member] sqft
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable square feet					134,000					101,000					79,000					33,000
Contract sale price					$ 23,000					$ 14,250	$ 15,750		$ 15,750							$ 8,750
Real Estate, Type of Property, Office								Office	Office		Office		Office
Real Estate, Type of property, Medical Office																		Medical Office	Medical Office
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues	0	1,187	347	2,472
Property expenses	0	(446)	(162)	(908)
Depreciation and amortization	0	(364)	0	(776)
Interest expense	0	(63)	0	(127)
Income from operations of properties sold or held for sale	$ 0	$ 314	$ 185	$ 661		$ 0	$ 74	$ 0	$ 118		$ 0	$ 225	$ 185	$ 514		$ 0	$ 15	$ 0	$ 29