Consolidated Statements Of Operations (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
REVENUE
Rental income	$ 154,308,000	$ 146,943,000	$ 460,136,000	$ 428,330,000
Other property income	3,480,000	9,007,000	9,661,000	17,842,000
Mortgage interest income	1,242,000	1,282,000	3,770,000	3,834,000
Total revenue	159,030,000	157,232,000	473,567,000	450,006,000
EXPENSES
Rental expenses	29,045,000	29,658,000	86,755,000	82,609,000
Real estate taxes	18,400,000	17,224,000	53,604,000	49,680,000
General and administrative	7,543,000	8,751,000	22,902,000	22,894,000
Depreciation and amortization	39,341,000	34,847,000	119,615,000	106,451,000
Total operating expenses	94,329,000	90,480,000	282,876,000	261,634,000
OPERATING INCOME	64,701,000	66,752,000	190,691,000	188,372,000
Other interest income	70,000	261,000	165,000	580,000
Interest expense	(25,762,000)	(28,218,000)	(80,314,000)	(85,744,000)
Early extinguishment of debt	0	0	(3,399,000)	0
Income from real estate partnerships	381,000	490,000	1,065,000	1,229,000
INCOME FROM CONTINUING OPERATIONS	39,390,000	39,285,000	108,208,000	104,437,000
DISCONTINUED OPERATIONS
Discontinued Operations - income	100,000	400,000	900,000	1,100,000
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	23,861,000	0	23,861,000	0
Results from discontinued operations	23,976,000	371,000	24,803,000	1,077,000
INCOME BEFORE GAIN ON SALE OF REAL ESTATE	63,366,000	39,656,000	133,011,000	105,514,000
Gain on sale of real estate	0	0	4,994,000	11,860,000
NET INCOME	63,366,000	39,656,000	138,005,000	117,374,000
Net income attributable to noncontrolling interests	(1,268,000)	(1,012,000)	(3,780,000)	(3,141,000)
NET INCOME ATTRIBUTABLE TO THE TRUST	62,098,000	38,644,000	134,225,000	114,233,000
Dividends on preferred shares	(136,000)	(136,000)	(406,000)	(406,000)
NET INCOME AVAILABLE FOR COMMON SHAREHOLDERS	61,962,000	38,508,000	133,819,000	113,827,000
EARNINGS PER COMMON SHARE, BASIC
Continuing operations	$ 0.57	$ 0.59	$ 1.58	$ 1.57
Discontinued Operations	$ 0.37	$ 0.01	$ 0.38	$ 0.02
Gain on sale of real estate	$ 0.00	$ 0.00	$ 0.08	$ 0.19
Earnings Per Share, Basic, Total	$ 0.94	$ 0.60	$ 2.04	$ 1.78
Weighted average common shares outstanding-basic	65,504	64,014	65,118	63,711
EARNINGS PER COMMON SHARE, DILUTED
Continuing operations	$ 0.57	$ 0.59	$ 1.58	$ 1.56
Discontinued Operations	$ 0.37	$ 0.01	$ 0.38	$ 0.02
Gain on sale of real estate	$ 0.00	$ 0.00	$ 0.08	$ 0.19
Earnings Per Share, Diluted, Total	$ 0.94	$ 0.60	$ 2.04	$ 1.77
Weighted average number of common shares-diluted	65,647	64,202	65,271	63,891
Comprehensive Income	62,195,000	36,804,000	146,854,000	108,087,000
Comprehensive Income Attributable to the Trust	$ 60,927,000	$ 35,792,000	$ 143,074,000	$ 104,946,000