Condensed Consolidated Statements Of Equity (USD $) In Thousands		Preferred Shares Of Beneficial Interest [Member]	Common Shares Of Beneficial Interest [Member]	Accumulated Additional Paid-In Capital [Member]	Net Income In Excess Of Less Than Accumulated Dividends [Member]	Accumulated Other Comprehensive Loss [Member]	Noncontrolling Interests [Member]	Total
Balance at Dec. 31, 2009		$ 8	$ 3,615	$ 1,958,975	$ (37,350)	$ (23,958)	$ 205,366	$ 2,106,656
Net income					22,411		1,381	23,792
Shares issued in exchange for noncontrolling interests			1	745			(746)
Shares issued under benefit plans			8	4,599				4,607
Dividends declared - common shares	[1]				(62,530)			(62,530)
Dividends declared - preferred shares	[2]				(16,426)			(16,426)
Distributions to noncontrolling interests							(7,718)	(7,718)
Contributions from noncontrolling interests							1,336	1,336
Consolidation of joint ventures							(18,573)	(18,573)
Other comprehensive income						1,328		1,328
Other, net				427	(1,312)		(88)	(973)
Balance at Jun. 30, 2010		8	3,624	1,964,746	(95,207)	(22,630)	180,958	2,031,499
Balance at Dec. 31, 2010		8	3,630	1,969,905	(151,780)	(21,774)	180,268	1,980,257
Net income					17,799		2,328	20,127
Shares issued under benefit plans			10	7,516				7,526
Dividends declared - common shares	[1]				(66,407)			(66,407)
Dividends declared - preferred shares	[2]				(16,426)			(16,426)
Distributions to noncontrolling interests							(7,259)	(7,259)
Contributions from noncontrolling interests							3,717	3,717
Other comprehensive income						948		948
Other, net				2,864	(1,312)		(2,449)	(897)
Balance at Jun. 30, 2011		$ 8	$ 3,640	$ 1,980,285	$ (218,126)	$ (20,826)	$ 176,605	$ 1,921,586

[1] Common dividend per share was $.52 and $.55 for the six months ended June 30, 2010 and 2011, respectively.

[2] Series D, E and F preferred dividend per share was $25.31, $86.88 and $81.25, respectively, for both the six months ended June 30, 2010 and 2011.