Condensed Consolidated Statements Of Equity (Unaudited) (USD $)		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		$ 1,687,978,000	$ 2,000	$ 3,683,000	$ 1,679,229,000	$ (300,537,000)	$ (4,202,000)	$ 309,803,000
Increase (Decrease) in Equity [Roll Forward]
Net Income		64,781,000				63,303,000		1,478,000
Shares issued under benefit plans		5,630,000		7,000	5,623,000
Dividends paid - common shares	[1]	(39,703,000)				(39,703,000)
Dividends paid - preferred shares	[2]	(2,438,000)				(2,438,000)
Distributions to noncontrolling interests		(2,351,000)						(2,351,000)
Acquisition of noncontrolling interests		0			10,932,000			(10,932,000)
Disposition of noncontrolling interests		(144,326,000)						(144,326,000)
Other comprehensive income (loss)		581,000					581,000
Other, net		(221,000)			51,000	(272,000)
Ending Balance at Mar. 31, 2014		1,569,931,000	2,000	3,690,000	1,695,835,000	(279,647,000)	(3,621,000)	153,672,000
Beginning Balance at Dec. 31, 2014		1,638,943,000	2,000	3,700,000	1,706,880,000	(212,960,000)	(12,436,000)	153,757,000
Increase (Decrease) in Equity [Roll Forward]
Net Income		49,222,000				47,647,000		1,575,000
Issuance of common shares, net		29,036,000		24,000	29,012,000
Shares issued under benefit plans		5,556,000		9,000	5,547,000
Shares issued in exchange for noncontrolling interests		0			111,000			(111,000)
Dividends paid - common shares	[1]	(42,476,000)				(42,476,000)
Dividends paid - preferred shares	[2]	(2,438,000)				(2,438,000)
Distributions to noncontrolling interests		(1,660,000)						(1,660,000)
Other comprehensive income (loss)		(523,000)					(523,000)
Other, net		(132,000)			254,000	(272,000)		(114,000)
Ending Balance at Mar. 31, 2015		$ 1,675,528,000	$ 2,000	$ 3,733,000	$ 1,741,804,000	$ (210,499,000)	$ (12,959,000)	$ 153,447,000

[1] Common dividend per share was $.345 and $.325 for the three months ended March 31, 2015 and 2014, respectively.

[2] Series F preferred dividend per share was $40.63 for both the three months ended March 31, 2015 and 2014.