Organization (Details)	9 Months Ended	3 Months Ended
	Sep. 30, 2011	Sep. 30, 2011 Office properties [Member] squarefeet	Sep. 30, 2011 Building [Member] Joint Venture [Member]	Sep. 30, 2011 Industrial buildings [Member]
Real Estate Properties [Line Items]
Number Of Wholly Owned Subsidiaries	2
Number of Real Estate Properties		79	5	2
Number of Metropolitan Areas	18
Square Footage of Real Estate Property		21,800,000
Real Estate Properties Leased, Percent		86.40%