Condensed Consolidated Statements Of Equity (USD $) In Thousands, unless otherwise specified		Total	Preferred Shares Of Beneficial Interest [Member]	Common Shares Of Beneficial Interest [Member]	Additional Paid-In Capital [Member]	Net Income Less Than Accumulated Dividends [Member]	Accumulated Other Comprehensive Loss [Member]	Noncontrolling Interests [Member]	6.75% Series D Preferred Shares [Member]	6.75% Series D Preferred Shares [Member] Preferred Shares Of Beneficial Interest [Member]	6.75% Series D Preferred Shares [Member] Additional Paid-In Capital [Member]	6.75% Series D Preferred Shares [Member] Net Income Less Than Accumulated Dividends [Member]	6.5% Series F Preferred Shares [Member]	6.5% Series F Preferred Shares [Member] Preferred Shares Of Beneficial Interest [Member]	6.5% Series F Preferred Shares [Member] Additional Paid-In Capital [Member]	6.5% Series F Preferred Shares [Member] Net Income Less Than Accumulated Dividends [Member]
Balance at Dec. 31, 2011		$ 1,823,582	$ 8	$ 3,641	$ 1,983,978	$ (304,504)	$ (27,743)	$ 168,202
Increase (Decrease) in Equity [Roll Forward]
Net Income		97,446				92,889		4,557
Shares issued under benefit plans		11,503		17	11,486
Dividends declared - common shares	[1]	(105,466)				(105,466)
Dividends declared - preferred shares	[2]	(24,639)				(24,639)
Distributions to noncontrolling interests		(10,119)						(10,119)
Contributions from noncontrolling interests		2,123						2,123
Other comprehensive income		1,804					1,804
Other, net		617			1,766	(1,968)		819
Balance at Sep. 30, 2012		1,796,851	8	3,658	1,997,230	(343,688)	(25,939)	165,582
Balance at Dec. 31, 2012		1,740,155	7	3,663	1,934,183	(335,980)	(24,743)	163,025
Increase (Decrease) in Equity [Roll Forward]
Net Income		211,384				170,328		41,056
Redemption of preferred shares									(75,000)	(3)	(72,755)	(2,242)	(200,000)	(2)	(184,296)	(15,702)
Shares issued under benefit plans		12,493		20	12,473
Dividends declared - common shares	[1]	(111,509)				(111,509)
Dividends declared - preferred shares	[2]	(14,760)				(14,760)
Distributions to noncontrolling interests		(13,455)						(13,455)
Contributions from noncontrolling interests		33,884						33,884
Other comprehensive income		9,596					9,596
Other, net		1,501			1,082	(703)		1,122
Balance at Sep. 30, 2013		$ 1,594,289	$ 2	$ 3,683	$ 1,690,687	$ (310,568)	$ (15,147)	$ 225,632

[1] Common dividend per share was $.915 and $.870 for the nine months ended September 30, 2013 and 2012, respectively.

[2] Series D preferred dividend per share was $13.08 and $37.97 for the nine months ended September 30, 2013 and 2012, respectively. Series E preferred dividend per share was $130.31 for the nine months ended September 30, 2012. Series F preferred dividend per share was $119.62 and $121.88 for the nine months ended September 30, 2013 and 2012, respectively.