Selected Quarterly Financial Data (Unaudited) Summary Of Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended											12 Months Ended
	Dec. 31, 2015		Sep. 30, 2015	Jun. 30, 2015		Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014		Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 192,507		$ 185,252	$ 181,461		$ 184,792	$ 176,377	$ 170,938		$ 167,947	$ 170,828	$ 744,012	$ 686,090	$ 637,413
Operating income	75,914		75,917	76,201		72,122	71,610	67,622		68,361	63,444	300,154	271,037	254,161
Net income	69,998	[1]	54,550	45,673	[1]	48,203	37,279	49,049	[1]	45,416	40,545	218,424	172,289	167,608
NET INCOME ATTRIBUTABLE TO THE TRUST	67,954	[1]	52,447	43,632	[1]	46,186	35,162	47,075	[1]	43,545	38,753	210,219	164,535	162,681
Net income available for common shareholders	$ 67,819	[1]	$ 52,311	$ 43,497	[1]	$ 46,051	$ 35,027	$ 46,939	[1]	$ 43,410	$ 38,618	$ 209,678	$ 163,994	$ 162,140
Earnings per common share-basic	$ 0.98	[1]	$ 0.75	$ 0.63	[1]	$ 0.67	$ 0.51	$ 0.69	[1]	$ 0.64	$ 0.58	$ 3.04	$ 2.42	$ 2.47
Earnings per common share-diluted	$ 0.97	[1]	$ 0.75	$ 0.63	[1]	$ 0.67	$ 0.51	$ 0.69	[1]	$ 0.64	$ 0.57	$ 3.03	$ 2.41	$ 2.46

[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.