Earnings Per Share (Schedule Of Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended										12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014		Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013		Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Income from continuing operations											$ 167,888	$ 137,811	$ 142,972
Less: Preferred share dividends											(541)	(541)	(541)
Less: Income from continuing operations attributable to noncontrolling interests											(7,754)	(4,927)	(4,307)
Less: Earnings allocated to unvested shares											(1,003)	(889)	(845)
Income from continuing operations available for common shareholders											158,590	131,454	137,279
Results from discontinued operations attributable to the Trust											0	24,803	1,400
Gain on sale of real estate											4,401	4,994	11,860
Net income available for common shareholders, basic and diluted											162,991	161,251	150,539
Weighted average common shares outstanding—basic											67,322	65,331	63,881
Stock options											170	152	175
Weighted average common shares outstanding—diluted											67,492	65,483	64,056
Continuing operations											$ 2.35	$ 2.01	$ 2.15
Discontinued operations											$ 0.00	$ 0.38	$ 0.02
Gain on sale of real estate											$ 0.07	$ 0.08	$ 0.19
EARNINGS PER COMMON SHARE, BASIC	$ 0.51	$ 0.69	[1]	$ 0.64	$ 0.58	$ 0.43	$ 0.94	[1]	$ 0.57	$ 0.53	$ 2.42	$ 2.47	$ 2.36
Continuing operations											$ 2.34	$ 2.00	$ 2.14
Discontinued operations											$ 0.00	$ 0.38	$ 0.02
Gain on sale of real estate											$ 0.07	$ 0.08	$ 0.19
EARNINGS PER COMMON SHARE, DILUTED	$ 0.51	$ 0.69	[1]	$ 0.64	$ 0.57	$ 0.42	$ 0.94		$ 0.57	$ 0.53	$ 2.41	$ 2.46	$ 2.35
Income from continuing operations attributable to the Trust											$ 160,134	$ 132,884	$ 138,665

[1] 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. Third quarter 2013 includes a $23.9 million gain on sale of two retail buildings as further discussed in Note 3.