Consolidated Statements of Beneficiaries' Equity (USD $) In Thousands, except Share data	Total	7.375% Series D Preferred Shares	Common Stock	Treasury Stock	Deferred Compensation Payable in Common Shares	Common Shares in Grantor Trust	Additional Paid-in Capital	Cumulative Earnings	Accumulated Other Comprehensive Income (Loss)	Cumulative Distributions	Non-Controlling Interests
Beginning Balance at Dec. 31, 2010	$ 1,977,774	$ 43	$ 1,343	$ (3,074)	$ 5,774	$ (5,774)	$ 2,671,217	$ 483,439	$ (1,945)	$ (1,301,521)	$ 128,272
Beginning Balance, shares at Dec. 31, 2010		4,300,000	134,601,796	116,679	291,281
Net income (loss)	(490)							(439)			(51)
Comprehensive income (loss)	(591)								(579)		(12)
Issuance of Common Shares of Beneficial Interest	2,305		2				2,303
Issuance of Common Shares of Beneficial Interest, shares			188,400
Equity issuance costs	(104)						(104)
Bonus Share Issuance	6			12	5	(5)		(6)
Bonus Share Issuance, shares				(463)	463
Vesting of Restricted Shares	144			2,462			(1,518)	(800)
Vesting of Restricted Shares, shares				(87,370)	9,043
Restricted Share Amortization	806						806
Restricted Performance Units Amortization	330						330
Share Option Amortization	(16)				(146)	146	(16)
Share Option Amortization, shares			(487)		(4,935)
Outperformance Plan Amortization	(55)						(55)
Outperformance Plan Amortization, shares			(1,684)
Share Issuance from/to Deferred Compensation Plan	344						344
Share Issuance from/to Deferred Compensation Plan, shares
Share Choice Plan Issuance	54						54
Adjustment to Non-controlling Interest	0						(210)				210
Preferred Share distributions	(1,998)									(1,998)
Distributions declared ($0.45), and ($0.15) per share in March 31, 2012 and March 31, 2011, respectively	(20,789)									(20,370)	(419)
Ending Balance at Mar. 31, 2011	1,957,720	43	1,345	(600)	5,633	(5,633)	2,673,151	482,194	(2,524)	(1,323,889)	128,000
Ending Balance, shares at Mar. 31, 2011		4,300,000	134,788,025	28,846	295,852
Beginning Balance at Dec. 31, 2011	1,889,696	43	1,424	0	5,631	(5,631)	2,776,197	477,338	(6,079)	(1,392,332)	33,105
Beginning Balance, shares at Dec. 31, 2011		4,300,000	142,690,755	0	292,646
Net income (loss)	9,336							9,202			134
Comprehensive income (loss)	75								74		1
Conversion of LP Units to Common Shares	(235)		0				149	(49)			(335)
Conversion of LP Units to Common Shares, shares			20,464
Bonus Share Issuance	387						387
Bonus Share Issuance, shares			35,703
Vesting of Restricted Shares	(89)		1				(90)
Vesting of Restricted Shares, shares			30,820		9,036
Restricted Share Amortization	678						678
Vesting of Restricted Performance Units	(1,328)		3				(1,331)
Vesting of Restricted Performance Units, shares			249,797
Restricted Performance Units Amortization	479						479
Exercise of Stock Options, shares	0
Share Option Amortization	376						376
Share Issuance from/to Deferred Compensation Plan	0				(195)	195
Share Issuance from/to Deferred Compensation Plan, shares			(5,389)		(8,560)
Adjustment to Non-controlling Interest	13						303				(290)
Preferred Share distributions	(1,998)									(1,998)
Distributions declared ($0.45), and ($0.15) per share in March 31, 2012 and March 31, 2011, respectively	(21,948)									(21,586)	(362)
Ending Balance at Mar. 31, 2012	$ 1,875,442	$ 43	$ 1,428	$ 0	$ 5,436	$ (5,436)	$ 2,777,148	$ 486,491	$ (6,005)	$ (1,415,916)	$ 32,253
Ending Balance, shares at Mar. 31, 2012		4,300,000	143,022,150	0	293,122