Equity And Accumulated Other Comprehensive Loss, Net (Narrative) (Details) (USD $)	9 Months Ended				0 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Dec. 31, 2012	Apr. 09, 2013 Series G Cumulative Convertible Preferred Units [Member] [Member]	Sep. 30, 2013 Series G Cumulative Convertible Preferred Units [Member] [Member]	Dec. 31, 2012 Series G Cumulative Convertible Preferred Units [Member] [Member]	Sep. 30, 2013 Series F Cumulative Convertible Preferred Units [Member]	Dec. 31, 2012 Series F Cumulative Convertible Preferred Units [Member]	Sep. 30, 2013 Series E Cumulative Convertible Preferred Units [Member]	Dec. 31, 2012 Series E Cumulative Convertible Preferred Units [Member]	Sep. 30, 2013 Series D Cumulative Convertible Preferred Units [Member]	Dec. 31, 2012 Series D Cumulative Convertible Preferred Units [Member]	Sep. 30, 2012 2011 Equity Distribution Agreements [Member]	Sep. 30, 2013 2011 Equity Distribution Agreements [Member]	Jun. 29, 2011 2011 Equity Distribution Agreements [Member]
Equity and Accumulated Other Comprehensive Income (Loss) [Line Items]
Net proceeds from sale of common stock														$ 62,700,000
Aggregate offering price of the distribution agreement maximum																400,000,000
Equity distribution agreements at an average price														$ 66.19
Payment of commissions to sales agents														600,000
Aggregate offering price remaining available for offer and sale															53,800,000
Gross proceeds from the issuance of common stock			894,221,000
Issuance of common shares														1,000,000
Preferred stock, issued					10,000,000	10,000,000	0	7,300,000	7,300,000	11,500,000	11,500,000	0	4,936,505
Preferred stock, dividend rate					5.875%	5.875%	5.875%	6.625%	6.625%	7.00%	7.00%	5.50%	5.50%
Gross proceeds from issuance of redeemable preferred stock					250,000,000
Preferred stock dividend per share amount					$ 1.46875	$ 1.469		$ 1.656		$ 1.750
Preferred stock, liquidation preference per share/unit					$ 25.00	$ 25	$ 25	$ 25	$ 25	$ 25	$ 25	$ 25	$ 25
Dividend and distribution amount					$ 0.334550
Preferred stock, redemption price per share						$ 25.00
Shares issued upon conversion						0.7532
Redemption value of OP units	134,900,000			161,500,000
Percentage of operating partnership common units issued	25.00%
Available indebtedness	17,800,000
Acquisition amount	$ 152,900,000	[1]

[1] Purchase prices are all in U.S. dollars and exclude capitalized closing costs on land acquisitions. Purchase prices for acquisitions outside the United States are based on the exchange rate at the date of acquisition.