Property Transactions (Properties Held for Sale) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Document Fiscal Year Focus	2013
Gain on sale of discontinued operations, net	$ 11,489	$ 18,407	$ 8,519
Third party management and leasing business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of discontinued operations, net	4,577	7,459	0
Tiffany Springs MarketCenter Kansas City [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of discontinued operations, net	3,697	0	0
Summary of sales in discontinued operations
Area of disposed real estate assets (square feet)	238,000
Sales price of property held for sale, discontinued operations	53,500
Lakeshore Park Plaza Birmingham [Member]
Summary of sales in discontinued operations
Area of disposed real estate assets (square feet)	197,000
Six Hundred University Park Place Birmingham [Member]
Summary of sales in discontinued operations
Area of disposed real estate assets (square feet)	123,000
The Avenue Forsyth Suburban Atlanta, GA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of discontinued operations, net	(77)	4,508	0
Summary of sales in discontinued operations
Area of disposed real estate assets (square feet)		524,000
Sales price of property held for sale, discontinued operations		119,000
The Avenue Collierville [Member]
Summary of sales in discontinued operations
Area of disposed real estate assets (square feet)		511,000
Sales price of property held for sale, discontinued operations		55,000
The Avenue Webb Gin Suburban Atlanta, GA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of discontinued operations, net	(2)	3,590	0
Summary of sales in discontinued operations
Area of disposed real estate assets (square feet)		322,000
Sales price of property held for sale, discontinued operations		59,600
Galleria 75 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of discontinued operations, net	0	569	0
Summary of sales in discontinued operations
Area of disposed real estate assets (square feet)		111,000
Sales price of property held for sale, discontinued operations		9,200
Cosmopolitan Center [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of discontinued operations, net	0	2,064	0
Summary of sales in discontinued operations
Area of disposed real estate assets (square feet)		51,000
Sales price of property held for sale, discontinued operations		7,000
Inhibitex Suburban Atlanta, GA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of discontinued operations, net	2,989	0	0
Summary of sales in discontinued operations
Area of disposed real estate assets (square feet)	51,000
King Mill Distribution Park- Building 3 Suburban Atlanta, GA [Member]
Summary of sales in discontinued operations
Area of disposed real estate assets (square feet)		796,000
Sales price of property held for sale, discontinued operations		28,300
Lakeside Ranch Business Park - Building 20 Dallas, TX [Member]
Summary of sales in discontinued operations
Area of disposed real estate assets (square feet)		749,000
Sales price of property held for sale, discontinued operations		28,400
Jefferson Mill Business Park - Building A Suburban Atlanta, GA [Member]
Summary of sales in discontinued operations
Area of disposed real estate assets (square feet)		459,000
Sales price of property held for sale, discontinued operations		22,000
One Georgia Center Atlanta, GA [Member]
Summary of sales in discontinued operations
Area of disposed real estate assets (square feet)		376,000
Sales price of property held for sale, discontinued operations		$ 48,600