Consolidated Statements of Beneficiaries' Equity (USD $) In Thousands, except Share data	Total	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	Series C Preferred Stock [Member]	Series D Preferred Stock [Member]
Beginning Balance at Dec. 31, 2009	$ 1,921,740	$ 43	$ 1,286	$ (7,205)	$ 5,549	$ (5,549)	$ 2,610,421	$ 501,384	$ (9,138)	$ (1,213,359)	$ 38,308
Beginning Balance, shares at Dec. 31, 2009		4,300,000	128,849,176	251,764	255,700
Net income (loss)	(17,606)							(17,074)			(532)
Comprehensive income (loss)	7,348								7,193		155
Issuance of Common Shares of Beneficial Interest	71,981		57				71,924
Issuance of Common Shares of Beneficial Interest, shares			5,742,268
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs	(1,214)						(1,214)
Noncontrolling Interest, Increase from Equity Issuance or Sale of Parent Equity Interest	77,732										77,732
Bonus Share Issuance	369			871	369	(369)		(502)
Bonus Share Issuance, shares				(32,607)	32,607
Vesting of Restricted Shares	(227)			2,304	103	(103)	(1,114)	(1,417)
Vesting of Restricted Shares, shares				(76,598)	8,989
Restricted Share Amortization	3,483						3,483
Restricted Performance Units Amortization	965						965
Conversion of LP Units to Common Shares	0			732				(266)			(466)
Conversion of LP Units to Common Shares, shares				(17,468)
Share Issuance from/to Deferred Compensation Plan	0				(282)	282
Share Issuance from/to Deferred Compensation Plan, shares			(2,409)		(9,035)
Share Option Amortization	1,131						1,131
Outperformance Plan Amortization	380						380
Stock Issued During Period, Value, Other	99			224	35	(35)		(125)
Stock Issued During Period, Shares, Other				(8,412)	3,020
Exercise of Stock Options	37						37
Exercise of Stock Options, shares	12,761		12,761
Adjustment to Non-controlling Interest	0						(14,796)				14,796
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	1,401							1,439			(38)
Preferred Share distributions	(7,992)									(7,992)
Preferred share redemption charge	0
Distributions declared ($0.60) per share in each of 2012, 2011, and 2010	(81,853)									(80,170)	(1,683)
Ending 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
Ending Balance, shares at Dec. 31, 2010		4,300,000	134,601,796	116,679	291,281
Net income (loss)	(4,715)							(4,500)			(215)
Comprehensive income (loss)	(4,346)								(4,134)		(212)
Issuance of Common Shares of Beneficial Interest	8,272		7				8,265
Issuance of Common Shares of Beneficial Interest, shares			679,285
Preferred Stock, Value, Issued		0										20	23
Preferred Stock, Shares Issued												2,000,000	2,300,000
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs	(377)						(345)				(32)
Bonus Share Issuance	6			12	6	(6)		(6)
Bonus Share Issuance, shares				(463)	463
Vesting of Restricted Shares	(350)		1	3,062			(1,818)	(1,595)
Vesting of Restricted Shares, shares			85,248	(116,216)	9,043
Restricted Share Amortization	2,937						2,937
Restricted Performance Units Amortization	1,679						1,679
Conversion of LP Units to Common Shares	0		72				85,966				(86,038)
Conversion of LP Units to Common Shares, shares			7,204,104
Share Issuance from/to Deferred Compensation Plan	(16)				(149)	149	(16)
Share Issuance from/to Deferred Compensation Plan, shares			(845)		(8,141)
Share Option Amortization	1,487						1,487
Outperformance Plan Amortization	123						123
Share Choice Plan Issuance Value	(55)						(55)
Share Choice Plan Issuance Shares			(1,684)
Stock Issued During Period, Value, Other	32						32
Stock Issued During Period, Shares, Other			2,672
Exercise of Stock Options	350		1				349
Exercise of Stock Options, shares	120,180		120,179
Adjustment to Non-controlling Interest	0						6,376				(6,376)
Preferred Share distributions	(7,992)									(7,992)
Preferred share redemption charge	0
Distributions declared ($0.60) per share in each of 2012, 2011, and 2010	(85,113)									(82,819)	(2,294)
Ending 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
Ending Balance, shares at Dec. 31, 2011		4,300,000	142,690,755	0	292,646
Net income (loss)	6,529							6,595			(66)
Comprehensive income (loss)	(10,026)								(9,839)		(187)
Preferred Stock, Value, Issued	96,850	40					96,810					0	0
Preferred Stock, Shares Issued		4,000,000										0	0
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs	(613)						(613)
Bonus Share Issuance	387						387
Bonus Share Issuance, shares			35,703
Stock Redeemed or Called During Period, Value	(103,448)	(43)					(103,405)
Stock Redeemed or Called During Period, Shares		(4,300,000)
Partners' Capital Account, Redemptions	(9,741)							(4,185)			(5,556)
Vesting of Restricted Shares	(1,385)		4				(1,389)
Vesting of Restricted Shares, shares			293,614		9,036
Restricted Share Amortization	3,271						3,271
Restricted Stock Award, Forfeitures	35							35
Restricted Performance Units Amortization	3,379						3,379
Conversion of LP Units to Common Shares	(167)		1				149	(49)			(268)
Conversion of LP Units to Common Shares, shares			20,464
Share Issuance from/to Deferred Compensation Plan	0				(279)	279
Share Issuance from/to Deferred Compensation Plan, shares			(5,564)		(10,937)
Share Option Amortization	1,636						1,636
Stock Issued During Period, Value, Other	15						15
Stock Issued During Period, Shares, Other			1,336
Exercise of Stock Options	976		2				974
Exercise of Stock Options, shares	230,294		230,294
Adjustment to Non-controlling Interest	0						4,281				(4,281)
Preferred Share distributions	(10,405)									(10,405)
Preferred share redemption charge	(4,052)									(4,052)
Distributions declared ($0.60) per share in each of 2012, 2011, and 2010	(87,926)									(86,417)	(1,509)
Stock Issued During Period, Shares, Vesting of restricted performance units			272,131
Stock Issued During Period, Value, Vesting of restricted performance units	(1,495)		3				(1,498)
Ending Balance at Dec. 31, 2012	1,773,516	40	1,434	0	5,352	(5,352)	2,780,194	479,734	(15,918)	(1,493,206)	21,238
Ending Balance, shares at Dec. 31, 2012		4,000,000	143,538,733	0	290,745
Beginning Balance at Sep. 30, 2012
Net income (loss)	(26,698)
Preferred Stock, Value, Issued	96,850											0	0
Preferred Stock, Shares Issued												0	0
Ending Balance at Dec. 31, 2012	$ 1,773,516			$ 0
Ending Balance, shares at Dec. 31, 2012				0