Equity, Capital and Other Interests Text (Details) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Preferred Stock, Shares Authorized		100,000,000	100,000,000
Additional Common Shares Authorized		13,000,000
Stock Issued During Period, Shares, New Issues		34,468,085	25,023,919	3,866,666
Average Price Per Common Share Issued			$ 60.59	$ 52.23
Stock Issued During Period, Value, New Issues			$ 192,300,000	$ 201,900,000
Payments of Stock Issuance Costs		1,047,000	39,359,000	3,596,000
Units Issued During Period New Issues			3,200,000	3,900,000
Common Stock Capital Shares Reserved For Future Issuance Under Share Offering Program		17,000,000
Common Shares Added To Atm Program		5,700,000
Shares not settled				500,000
Consideration From Shares Not Settled				28,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized		12,980,741	12,980,741
Stock Repurchase Program, Remaining Authorized Repurchase Amount	464,600,000
Stock Repurchase Program, Number of Shares Authorized to be Repurchased		13,000,000
Payments for Repurchase of Preferred Stock and Preference Stock		0	150,000,000	0
Issuance Of Units To Noncontrolling Interests			1,081,797
Price Per Unit Issued			$ 61.57
Properties acquired			1
Proceeds from Issuance of Common Limited Partners Units			66,600,000
Partially Owned Properties Acquired Properties			1	3
Partially Owned Units Acquired Units				1,351
Change in Paid In Capital			1,300,000	(4,800,000)
Reduction In Partially Owned Properties			1,300,000	8,000,000
Archstone Transaction [Member]
Stock Issued During Period, Shares, New Issues		34,468,085
Average Price Per Common Share Issued		$ 55.99
Stock Issued During Period, Value, New Issues		1,900,000,000
Units Issued During Period New Issues		34,468,085
Public Offering [Member]
Stock Issued During Period, Shares, New Issues			21,850,000
Average Price Per Common Share Issued			$ 54.75
Stock Issued During Period, Value, New Issues			1,200,000,000
Payments of Stock Issuance Costs			35,900,000
Units Issued During Period New Issues			21,850,000
General And Limited Partner [Member]
Stock Issued During Period Shares		34,468,085	25,023,919
Series N Preferred Stock [Member]
Payments for Repurchase of Preferred Stock and Preference Stock		150,000,000
Premium on Redemption of Preferred Shares Preference Units Original Issuance		5,100,000
Partner Buyout [Member]
Purchase Price, Business Acquisition, Cost of Acquired Entity				$ 12,800,000
ATM Program [Member]
Stock Issued During Period, Shares, New Issues			3,200,000
ATM Program [Member] | General And Limited Partner [Member]
Stock Issued During Period Shares				3,866,666