Equity, Capital and Other Interests Text (Details) (USD $)	9 Months Ended
	Sep. 30, 2012
Common Stock Capital Shares Reserved For Future Issuance Under Share Offering Program	17,000,000
Common Shares Added To Atm Program	5,700,000
Stock Issued During Period, Shares, New Issues	3,200,000
Average Price Per Common Share Issued	$ 60.59
Stock Issued During Period, Value, New Issues	$ 192,300,000
Units Issued During Period New Issues	3,200,000
Additional Common Shares Authorized	6,000,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	464,600,000
Units Issued To Noncontrolling Interests	1,081,797
Price Per Unit Issued	$ 61.57
Proceeds from Issuance of Common Limited Partners Units	66,600,000
Partially owned development projects acquired from outside partner	1
Increase To Reduction Of Paid In Capital	(1,200,000)
Business Acquisition, Cost of Acquired Entity, Transaction Costs	100,000
Reduction In Partially Owned Properties	$ 1,300,000
General And Limited Partner [Member]
Units Issued To Noncontrolling Interests	1,081,797