Discontinued Operations (Details) (USD $)	3 Months Ended		0 Months Ended	3 Months Ended	0 Months Ended	3 Months Ended
	Mar. 31, 2014 sqft	Mar. 31, 2013	Jan. 17, 2014 Woodbranch sqft	Mar. 31, 2014 Woodbranch sqft	Jan. 31, 2014 Mesa Corporate Center sqft	Mar. 31, 2014 Mesa Corporate Center sqft
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of real estate from discontinued operations	$ 10,463,000	$ 542,000		$ 9,974,000	$ 489,000	$ 489,000
Net proceeds from the sale			13,900,000		12,100,000
Area of real estate property (in square feet)	3,073,000		109,000	109,000	106,000	106,000
Gross proceeds from sale of real estate discontinued operations			$ 15,000,000		$ 13,200,000