Discontinued Operations (Details) (USD $)	3 Months Ended		9 Months Ended		0 Months Ended	9 Months Ended	0 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Jan. 17, 2014 Woodbranch Building	Sep. 30, 2014 Woodbranch Building	Jan. 31, 2014 Mesa Corporate Center	Sep. 30, 2014 Mesa Corporate Center
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gross proceeds from sale of real estate discontinued operations					$ 15,000,000		$ 13,200,000
Net proceeds from the sale					13,900,000		12,100,000
Gain on sale of real estate from discontinued operations	$ 0	$ 11,545,000	$ 10,463,000	$ 12,087,000		$ 9,974,000		$ 489,000