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, 2013	Sep. 30, 2013		Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]
Income from continuing operations										$ 137,811	$ 142,972	$ 130,319
Less: Preferred share dividends										(541)	(541)	(541)
Less: Income from continuing operations attributable to noncontrolling interests										(4,927)	(4,307)	(5,475)
Less: Earnings allocated to unvested shares										(889)	(845)	(705)
Income from continuing operations available for common shareholders										131,454	137,279	123,598
Results from discontinued operations attributable to the Trust										24,803	1,400	19,073
Gain on sale of real estate										4,994	11,860	0
Net income available for common shareholders, basic and diluted										161,251	150,539	142,671
Weighted average common shares outstanding-basic										65,331	63,881	62,438
Stock options										152	175	165
Weighted average common shares outstanding-diluted										65,483	64,056	62,603
Continuing operations										$ 2.01	$ 2.15	$ 1.98
Discontinued operations										$ 0.38	$ 0.02	$ 0.31
Gain on sale of real estate										$ 0.08	$ 0.19	$ 0.00
Earnings Per Share, Basic, Total	$ 0.43	$ 0.94	[1]	$ 0.57	$ 0.53	$ 0.58	$ 0.60	$ 0.51	$ 0.67	$ 2.47	$ 2.36	$ 2.29
Continuing operations										$ 2.00	$ 2.14	$ 1.97
Discontinued operations										$ 0.38	$ 0.02	$ 0.31
Gain on sale of real estate										$ 0.08	$ 0.19	$ 0.00
Earnings Per Share, Diluted, Total	$ 0.42	$ 0.94	[1]	$ 0.57	$ 0.53	$ 0.58	$ 0.60	$ 0.51	$ 0.67	$ 2.46	$ 2.35	$ 2.28
Income from continuing operations attributable to the Trust										$ 132,884	$ 138,665	$ 124,844

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