Commitments And Contingencies (Details) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2012 Number_of_Properties	Dec. 31, 2008 Number_of_Properties	Dec. 31, 2011
Commitments And Contingencies [Line Items]
Amount accounts are insured by Federal Deposit Insurance Corporation	$ 250,000
Number of consolidated properties containing asbestos	20
Commitments for future capital contributions related to our investments in our Funds	38,500,000
Number of Properties Contributed to our Unconsolidated Funds - 2008		6
Term loan under guarantee	3,256,140,000		3,623,096,000
Maximum future payments under the swap agreement	2,600,000
Number of tenants exceeding ten percent of our total rental revenue and tenant recoveries	0
Percentage of total rental revenue and tenant recoveries	10.00%
Guarantee Obligations [Member]
Commitments And Contingencies [Line Items]
Term loan under guarantee		365,000,000