Equity, Capital and Other Interests Text (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Additional Common Shares Authorized	13,000,000
Stock Issued During Period, Shares, New Issues	0	34,468,085	25,023,919
Acquisition of Archstone Common Shares Issued	$ 0	$ 1,929,868,000	$ 0
Average Price Per Common Share Issued			$ 60.59
Units Issued During Period New Issues			3,200,000
Stock Issued During Period, Value, New Issues			192,300,000
Payments of Stock Issuance Costs	41,000	1,047,000	39,359,000
Stock Repurchase Program, Number of Shares Authorized to be Repurchased	13,000,000
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased	12,968,760
Stock Repurchased and Retired During Period, Shares	(31,240)	0	0
Treasury Stock Acquired, Average Cost Per Share	$ 56.87
OP units repurchased and retired	1,777,000	0	0
Redemption of Preferred Shares	0	0	150,000,000
Issuance Of Units To Noncontrolling Interests			1,081,797
Proceeds from Issuance of Common Limited Partners Units			66,600,000
Price Per Unit Issued			$ 61.57
Properties acquired			1
Partially Owned Properties Acquired Properties	1		1
Partially Owned Units Acquired Units	268
Change in Paid In Capital	(2,300,000)		1,300,000
Reduction In Partially Owned Properties	2,200,000		1,300,000
Reduction In Other Liabilities	1,000,000
Archstone Transaction [Member]
Stock Issued During Period, Shares, New Issues		34,468,085
Acquisition of Archstone Common Shares Issued		1,929,868,000
Average Price Per Common Share Issued		$ 55.99
Units Issued During Period New Issues		34,468,085
Stock Issued During Period, Value, New Issues		1,200,000,000
Public Offering [Member]
Stock Issued During Period, Shares, New Issues			21,850,000
Average Price Per Common Share Issued			$ 54.75
Units Issued During Period New Issues			21,850,000
Stock Issued During Period, Value, New Issues			1,200,000,000
Payments of Stock Issuance Costs			35,900,000
Series N Preferred Stock [Member]
Redemption of Preferred Shares			150,000,000
Premium on redemption of Preferred Shares - original issuance costs			5,100,000
Preferred Stock Preference Units Dividend Rate Percentage	6.48%	6.48%	6.48%
Series P [Domain]
Preferred Stock Preference Units Dividend Rate Percentage	3.00%
Liquidation Value Preferred Interests	18,400,000
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage	95.00%
Partner Buyout [Member]
Purchase Price, Business Acquisition, Cost of Acquired Entity	$ 5,500,000
ATM Program [Member]
Stock Issued During Period, Shares, New Issues			3,200,000