Dispositions (Summary of Disposition Activity) (Details) (USD $)	9 Months Ended
	Sep. 30, 2012 property sqft		Dec. 31, 2011 sqft	Jan. 31, 2011 sqft
Acquisitions And Dispositions [Line Items]
Square Feet/Acres	16,700,000		3,900,000	2,600,000
Gross Sales Price	$ 62,089,000
Non-core properties under evaluation to sell	26
Income Producing Property Sold [Member]
Acquisitions And Dispositions [Line Items]
Gross Sales Price	60,429,000
Outparcels Sold [Member]
Acquisitions And Dispositions [Line Items]
Gross Sales Price	1,660,000
Mortgage Debt [Member]
Acquisitions And Dispositions [Line Items]
Debt repaid by buyer	27,200,000
Charlotte [Member] | Income Producing Property Sold [Member] | Laurel Walk Apartments [Member]
Acquisitions And Dispositions [Line Items]
Disposal Date	Mar. 30, 2012
Square Feet/Acres	106,480
Gross Sales Price	6,000,000
Commerce [Member] | Income Producing Property Sold [Member] | Commerce Crossing [Member]
Acquisitions And Dispositions [Line Items]
Disposal Date	Mar. 30, 2012
Square Feet/Acres	100,668
Gross Sales Price	600,000
San Francisco [Member] | Income Producing Property Sold [Member] | 222 Sutter Street [Member]
Acquisitions And Dispositions [Line Items]
Disposal Date	Mar. 15, 2012
Square Feet/Acres	128,595
Gross Sales Price	53,829,000	[1]
Norcross [Member] | Outparcels Sold [Member] | Market Place - IHOP [Member]
Acquisitions And Dispositions [Line Items]
Disposal Date	Feb. 27, 2012
Square Feet/Acres	0.35	[2]
Gross Sales Price	885,000
Lafayette Parish [Member] | Outparcels Sold [Member] | Grand Marche (Ground Lease) [Member]
Acquisitions And Dispositions [Line Items]
Disposal Date	Jan. 20, 2012
Square Feet/Acres	200,585
Gross Sales Price	$ 775,000

[1] Includes $27.2 million of mortgage debt repaid by the buyer at closing.

[2] In acres.