Organization And Basis Of Presentation (Details)	12 Months Ended
	Dec. 31, 2012 state sqft property
Real Estate Properties [Line Items]
Number of properties owned or investment interests	278
Aggregate square feet of the property owned or investment interest	31,700,000
Number of states where properties are located	6
Office And Office/Flex Buildings [Member]
Real Estate Properties [Line Items]
Number of properties owned or investment interests	258
Aggregate square feet of the property owned or investment interest	31,200,000
Unconsolidated Joint Venture Office Buildings [Member]
Real Estate Properties [Line Items]
Number of properties owned or investment interests	5
Aggregate square feet of the property owned or investment interest	800,000
Industrial/Warehouse Facilities [Member]
Real Estate Properties [Line Items]
Number of properties owned or investment interests	6
Aggregate square feet of the property owned or investment interest	387,400
Unconsolidated Joint Venture Multi-Family Properties [Member]
Real Estate Properties [Line Items]
Number of properties owned or investment interests	6
Number of units	1,769
Retail [Member]
Real Estate Properties [Line Items]
Number of properties owned or investment interests	4
Aggregate square feet of the property owned or investment interest	98,800
Unconsolidated Joint Venture Retail Buildings [Member]
Real Estate Properties [Line Items]
Number of properties owned or investment interests	2
Aggregate square feet of the property owned or investment interest	81,500
Unconsolidated Joint Venture Hotel [Member]
Real Estate Properties [Line Items]
Number of properties owned or investment interests	1
Number of units	350
Land [Member]
Real Estate Properties [Line Items]
Number of properties owned or investment interests	3