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		55,399				52,616		2,783
Shares issued under benefit plans		8,276		12	8,264
Dividends declared - common shares	[1]	(70,278)				(70,278)
Dividends declared - preferred shares	[2]	(16,426)				(16,426)
Distributions to noncontrolling interests		(7,333)						(7,333)
Contributions from noncontrolling interests		2,123						2,123
Other comprehensive income		1,189					1,189
Other, net		737			1,109	(1,312)		940
Balance at Jun. 30, 2012		1,797,269	8	3,653	1,993,351	(339,904)	(26,554)	166,715
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		148,995				109,786		39,209
Redemption of preferred shares									(75,000)	(3)	(72,755)	(2,242)	(200,000)	(2)	(184,296)	(15,702)
Shares issued under benefit plans		11,355		20	11,335
Dividends declared - common shares	[1]	(74,317)				(74,317)
Dividends declared - preferred shares	[2]	(12,322)				(12,322)
Distributions to noncontrolling interests		(8,241)						(8,241)
Contributions from noncontrolling interests		10,182						10,182
Other comprehensive income		9,079					9,079
Other, net		1,464			811	(431)		1,084
Balance at Jun. 30, 2013		$ 1,551,350	$ 2	$ 3,683	$ 1,689,278	$ (331,208)	$ (15,664)	$ 205,259

[1] Common dividend per share was $.610 and $.580 for the six months ended June 30, 2013 and 2012, respectively.

[2] Series D preferred dividend per share was $13.08 and $25.31 for the six months ended June 30, 2013 and 2012, respectively. Series E preferred dividend per share was $86.88 for the six months ended June 30, 2012. Series F preferred dividend per share was $78.99 and $81.25 for the six months ended June 30, 2013 and 2012, respectively.