Equity, Capital and Other Interests Text (Details) (USD $)	6 Months Ended
	Jun. 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	2,078,310
Average Price Per Common Share Issued	$ 59.47
Stock Issued During Period, Value, New Issues	$ 123,601,393
Units Issued During Period New Issues	2,078,310
Additional Common Shares Authorized	7,094,004
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	66,606,241
Partially owned development projects acquired from outside partner	1
Increase To Reduction Of Paid In Capital	(1,219,009)
Business Acquisition, Cost of Acquired Entity, Transaction Costs	0
Reduction In Partially Owned Properties	$ 1,305,993
General And Limited Partner [Member]
Units Issued To Noncontrolling Interests	1,081,797