Organization And Basis Of Presentation (Details)	9 Months Ended
	Sep. 30, 2011 sqft years
Number of properties owned or investment interests	278
Aggregate square feet of the property owned or investment interest	32,400,000
Number of locations of properties	5
Office And Office/Flex Buildings [Member]
Number of properties owned or investment interests	266
Aggregate square feet of the property owned or investment interest	32,000,000
Office Buildings [Member]
Number of properties owned or investment interests	8
Aggregate square feet of the property owned or investment interest	1,200,000
Industrial/Warehouse Facilities [Member]
Number of properties owned or investment interests	6
Aggregate square feet of the property owned or investment interest	387,400
Retail [Member]
Number of properties owned or investment interests	2
Aggregate square feet of the property owned or investment interest	17,300
Hotels [Member]
Number of properties owned or investment interests	1
Land Leased [Member]
Number of properties owned or investment interests	3