Condensed Consolidated Statements Of Equity (USD $) In Thousands		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]	Total
Balance at Dec. 31, 2010		$ 8	$ 3,630	$ 1,969,905	$ (151,780)	$ (21,774)	$ 180,268	$ 1,980,257
Net Income					16,096		1,092	17,188
Shares issued under benefit plans			6	3,824				3,830
Dividends declared - common shares	[1]				(33,178)			(33,178)
Dividends declared - preferred shares	[2]				(8,213)			(8,213)
Distributions to noncontrolling interests							(4,438)	(4,438)
Contributions from noncontrolling interests							1,600	1,600
Other comprehensive income						730		730
Other, net				2,233	(656)		(1,775)	(198)
Balance at Mar. 31, 2011		8	3,636	1,975,962	(177,731)	(21,044)	176,747	1,957,578
Balance at Dec. 31, 2011		8	3,641	1,983,978	(304,504)	(27,743)	168,202	1,823,582
Net Income					21,197		1,441	22,638
Shares issued under benefit plans			8	4,707				4,715
Dividends declared - common shares	[1]				(35,120)			(35,120)
Dividends declared - preferred shares	[2]				(8,213)			(8,213)
Distributions to noncontrolling interests							(3,756)	(3,756)
Other comprehensive income						675		675
Other, net				513	(656)		(119)	(262)
Balance at Mar. 31, 2012		$ 8	$ 3,649	$ 1,989,198	$ (327,296)	$ (27,068)	$ 165,768	$ 1,804,259

[1] Common dividend per share was $.290 and $.275 for the three months ended March 31, 2012 and 2011, respectively.

[2] Series D, E and F preferred dividend per share was $12.66, $43.44 and $40.63, respectively, for both the three months ended March 31, 2012 and 2011.