Earnings Per Share (Schedule Of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended											12 Months Ended
	Dec. 31, 2015	[1]	Sep. 30, 2015	Jun. 30, 2015	[1]	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	[1]	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Income from continuing operations												$ 190,094	$ 167,888	$ 137,811
Less: Preferred share dividends												(541)	(541)	(541)
Less: Income from continuing operations attributable to noncontrolling interests												(8,205)	(7,754)	(4,927)
Less: Earnings allocated to unvested shares												(797)	(1,003)	(889)
Income from continuing operations available for common shareholders												180,551	158,590	131,454
Results from discontinued operations attributable to the Trust												0	0	24,803
Gain on sale of real estate												28,330	4,401	4,994
Net income available for common shareholders, basic and diluted												$ 208,881	$ 162,991	$ 161,251
Weighted average common shares outstanding—basic												68,797	67,322	65,331
Stock options												184	170	152
Weighted average common shares outstanding—diluted												68,981	67,492	65,483
Continuing operations												$ 2.63	$ 2.35	$ 2.01
Discontinued operations												0.00	0.00	0.38
Gain on sale of real estate												0.41	0.07	0.08
EARNINGS PER COMMON SHARE, BASIC	$ 0.98		$ 0.75	$ 0.63		$ 0.67	$ 0.51	$ 0.69		$ 0.64	$ 0.58	3.04	2.42	2.47
Continuing operations												2.62	2.34	2.00
Discontinued operations												0.00	0.00	0.38
Gain on sale of real estate												0.41	0.07	0.08
EARNINGS PER COMMON SHARE, DILUTED	$ 0.97		$ 0.75	$ 0.63		$ 0.67	$ 0.51	$ 0.69		$ 0.64	$ 0.57	$ 3.03	$ 2.41	$ 2.46
Income from continuing operations attributable to the Trust												$ 181,889	$ 160,134	$ 132,884

[1] (1)Second and fourth quarter 2015 include an $11.5 million and $16.8 million gain on sale, respectively, from our Houston Street and Courtyard Shops properties as further discussed in Note 3. Third quarter 2014 includes a $4.4 million gain on sale reflecting our share of the Partnership's sale of Pleasant Shops as further discussed in Note 5.