Condensed Consolidated Statements of Equity (Unaudited) - USD ($) $ in Thousands		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]
Beginning Balance at Dec. 31, 2013		$ 1,687,978	$ 2	$ 3,683	$ 1,679,229	$ (300,537)	$ (4,202)	$ 309,803
Increase (Decrease) in Equity [Roll Forward]
Net Income		203,964				199,028		4,936
Shares issued under benefit plans		9,687		10	9,677
Dividends paid - common shares	[1]	(119,163)				(119,163)
Dividends paid - preferred shares	[2]	(7,314)				(7,314)
Distributions to noncontrolling interests		(5,939)						(5,939)
Contributions from noncontrolling interests		980						980
Other comprehensive income		1,824					1,824
Acquisition of noncontrolling interests		0			11,015			(11,015)
Disposition of noncontrolling interests		(144,263)						(144,263)
Other, net		(506)			499	(816)		(189)
Ending Balance at Sep. 30, 2014		1,627,248	2	3,693	1,700,420	(228,802)	(2,378)	154,313
Beginning Balance at Dec. 31, 2013		1,687,978	2	3,683	1,679,229	(300,537)	(4,202)	309,803
Ending Balance at Dec. 31, 2014		1,638,943	2	3,700	1,706,880	(212,960)	(12,436)	153,757
Increase (Decrease) in Equity [Roll Forward]
Net Income		132,196				127,077		5,119
Redemption of preferred shares		(150,000)	(2)		(140,311)	(9,687)
Issuance of common shares, net		40,331		34	40,297
Shares issued under benefit plans		8,062		10	8,052
Shares issued in exchange for noncontrolling interests		0			111			(111)
Dividends paid - common shares	[1]	(127,993)				(127,993)
Dividends paid - preferred shares	[2]	(3,873)				(3,873)
Distributions to noncontrolling interests		(4,541)						(4,541)
Contributions from noncontrolling interests		1,318						1,318
Other comprehensive income		3,407					3,407
Other, net		(486)			279	43		(808)
Ending Balance at Sep. 30, 2015		$ 1,537,364	$ 0	$ 3,744	$ 1,615,308	$ (227,393)	$ (9,029)	$ 154,734

[1] Common dividend per share was $1.04 and $.98 for the nine months ended September 30, 2015 and 2014, respectively.

[2] Series F preferred dividend per share was $64.55 and $121.88 for the nine months ended September 30, 2015 and 2014, respectively.