Property Transactions Property Transactions (Held for Sale) (Details)	Aug. 08, 2014 sqft	Sep. 30, 2014 Six Hundred University Park Place Birmingham [Member] sqft	Dec. 31, 2013 Six Hundred University Park Place Birmingham [Member] sqft	Sep. 30, 2014 777 Main Fort Worth, TX [Member] sqft	Sep. 30, 2014 Mahan Village LLC [Member] sqft	Sep. 30, 2014 Lakeshore Park Plaza Birmingham [Member] sqft	Dec. 31, 2013 Lakeshore Park Plaza Birmingham [Member] sqft
Long Lived Assets Held-for-sale [Line Items]
Area of Real Estate Property	698,000	123,000	123,000	980,000	147,000	197,000	197,000