Consolidated Statements of Beneficiaries' Equity (USD $) In Thousands, except Share data	Total	Total Preferred Shares	Series C Preferred Stock [Member]	Series E Preferred Stock [Member]	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)	(6,724)									(6,508)			(216)
Comprehensive income (loss)	(539)										(529)		(10)
Issuance of Common Shares of Beneficial Interest	8,272				7				8,265
Issuance of Common Shares of Beneficial Interest, shares					679,285
Equity issuance costs	260								234				26
Conversion of LP Units to Common Shares	0				1				1,098				(1,099)
Conversion of LP Units to Common Shares, shares					92,992
Bonus Share Issuance	6					12	5	(5)		(6)
Bonus Share Issuance, shares						(463)	463
Vesting of Restricted Shares	(355)				1	3,062			(1,820)	(1,598)
Vesting of Restricted Shares, shares					85,248	(116,216)	9,043
Restricted Share Amortization	1,519								1,519
Restricted Performance Units Amortization	780								780
Exercise of Stock Options	429				1				428
Exercise of Stock Options, shares					76,887
Share Option Amortization	728								728
Outperformance Plan Amortization	109								109
Outperformance Plan Amortization, shares
Share Issuance from/to Deferred Compensation Plan	(16)						(42)	42	(16)
Share Issuance from/to Deferred Compensation Plan, shares					(487)		4,935
Share Choice Plan Issuance Shares					1,684
Share Choice Plan Issuance	(55)								(55)
Stock Issued During Period, Value, Other	32								32
Stock Issued During Period, Shares, Other					2,672
Adjustment to Non-controlling Interest	0								2,679				(2,679)
Preferred Share distributions	(3,996)											(3,996)
Preferred share redemption charge	0
Distributions declared ($0.30), and ($0.30) per share in June 30, 2012 and June 30, 2011, respectively	(41,660)											(40,836)	(824)
Ending Balance at Jun. 30, 2011	1,936,044	43			1,353	0	5,737	(5,737)	2,684,730	475,327	(2,474)	(1,346,353)	123,418
Ending Balance, shares at Jun. 30, 2011		4,300,000			135,536,709	0	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)	16,138									15,973			165
Comprehensive income (loss)	(10,564)										(10,370)		(194)
Preferred Stock, Shares Issued		2,300,000	0	4,000,000
Preferred Stock, Value, Issued	96,850	23	0	40
Preferred Stock, Including Additional Paid in Capital, Net of Discount									96,810
Equity issuance costs	(610)								(610)
Stock Redeemed or Called During Period, Shares			(2,000,000)
Additional Paid in Capital, Preferred Stock									(47,890)
Stock Redeemed or Called During Period, Value	(47,910)		(20)
Conversion of LP Units to Common Shares	(228)								149	(45)			(332)
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	(1,292)				3				(1,295)
Vesting of Restricted Shares, shares					280,851		9,036
Restricted Share Amortization	1,426								1,426
Vesting of Restricted Performance Units	(1,329)				3				(1,332)
Vesting of Restricted Performance Units, shares					249,797
Restricted Performance Units Amortization	1,205								1,205
Exercise of Stock Options	275				1				274
Exercise of Stock Options, shares	94,429				94,429
Share Option Amortization	747								747
Share Issuance from/to Deferred Compensation Plan	0						195	(195)
Share Issuance from/to Deferred Compensation Plan, shares					5,389		8,560
Stock Issued During Period, Value, Other	15								15
Stock Issued During Period, Shares, Other					1,336
Adjustment to Non-controlling Interest	13								392				(379)
Preferred Share distributions	(5,047)											(5,047)
Preferred share redemption charge	(2,090)											(2,090)
Distributions declared ($0.30), and ($0.30) per share in June 30, 2012 and June 30, 2011, respectively	(43,953)											(43,193)	(760)
Ending Balance at Jun. 30, 2012	1,893,729	63			1,431	0	5,436	(5,436)	2,826,475	493,266	(16,449)	(1,442,662)	31,605
Ending Balance, shares at Jun. 30, 2012		6,300,000			143,367,946	0	293,122
Beginning Balance at Mar. 31, 2012
Net income (loss)	6,802
Comprehensive income (loss)	(10,639)
Preferred Stock, Shares Issued		2,300,000		4,000,000
Preferred Stock, Value, Issued	96,850	23		40
Preferred share redemption charge	(2,090)
Ending Balance at Jun. 30, 2012	$ 1,893,729	$ 63				$ 0
Ending Balance, shares at Jun. 30, 2012		6,300,000				0