Earnings Per Share (Schedule Of Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]
Income from continuing operations	$ 44,648	$ 39,390	$ 130,609	$ 108,208
Less: Preferred share dividends	(136)	(136)	(406)	(406)
Less: Income from continuing operations attributable to noncontrolling interests	(1,974)	(1,268)	(5,637)	(3,780)
Less: Earnings allocated to unvested shares	(264)	(278)	(739)	(659)
Income from continuing operations available for common shareholders	42,274	37,708	123,827	103,363
Results from discontinued operations attributable to the Trust	0	23,976	0	24,803
Gain on sale of real estate	4,401	0	4,401	4,994
Net income available for common shareholders, basic and diluted	46,675	61,684	128,228	133,160
Weighted average common shares outstanding—basic	67,559	65,504	67,095	65,118
Stock options	173	143	166	153
Weighted average common shares outstanding—diluted	67,732	65,647	67,261	65,271
Continuing operations	$ 0.62	$ 0.57	$ 1.84	$ 1.58
Discontinued operations	$ 0.00	$ 0.37	$ 0.00	$ 0.38
Gain on sale of real estate	$ 0.07	$ 0.00	$ 0.07	$ 0.08
Earnings per common share, basic, total	$ 0.69	$ 0.94	$ 1.91	$ 2.04
Continuing operations	$ 0.62	$ 0.57	$ 1.84	$ 1.58
Discontinued operations	$ 0.00	$ 0.37	$ 0.00	$ 0.38
Gain on sale of real estate	$ 0.07	$ 0.00	$ 0.07	$ 0.08
Earnings per common share, diluted, total	$ 0.69	$ 0.94	$ 1.91	$ 2.04
Income from continuing operations attributable to the Trust	$ 42,674	$ 38,122	$ 124,972	$ 104,428