Discontinued Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 1500 Sunday Drive [Member]	Mar. 31, 2013 Peninsula Business Center I and II [Member]	Mar. 31, 2013 Sun Trust Bank Building [Member]	Mar. 31, 2013 Lake Point and SunTrust Office [Member]	Dec. 31, 2012 Willowbrook Plaza [Member]	Mar. 31, 2012 Settlers Ridge Phase II [Member]	Mar. 31, 2012 Oak Hollow Square [Member]	Dec. 31, 2012 Hickory Hollow Mall [Member]	Dec. 31, 2012 Towne Mall [Member]	Sep. 30, 2012 Massard Crossing [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales of Real Estate			$ 8,300	$ 5,250			$ 24,450	$ 19,144	$ 14,247	$ 1,000	$ 950	$ 7,803
Gain on (loss) discontinued operations	781	911	(634)	590		824
Gross sales price					30,875
Proceeds from Sale of Real Estate			7,862	5,121		30,490	24,171	18,951	13,796	966	892	7,432
Gain (Loss) on Disposition of Real Estate, Discontinued Operations								883	255
Revenues of discontinued operations	434	4,613
Assets of Disposal Group, Including Discontinued Operation	$ 42,693