Consolidated Statements of Beneficiaries' Equity (USD $) In Thousands, except Share data	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Deferred Compensation, Share-based Payments [Member]	Common Stock In Grantor Trust [Member]	Cumulative Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Cumulative Distributions [Member]	Noncontrolling Interest [Member]
Beginning Balance at Dec. 31, 2013	$ 1,921,435	$ 40	$ 1,566	$ 2,971,596	$ 5,407	$ (5,407)	$ 522,528	$ (2,995)	$ (1,592,515)	$ 21,215
Beginning Balance, Shares at Dec. 31, 2013		4,000,000	156,731,993		312,279
Net income (loss)	(2,245)						(2,213)			(32)
Other comprehensive loss	(920)							(910)		(10)
Equity Issuance Costs	(52)			(52)
Share Based Compensation Activity, Shares			108,347
Share Based Compensation Activity, Value	2,651		1	2,643			7
Share Issuance from/to Deferred Compensation Plan, Shares			76,561		72,292
Share issuance from/to Deferred Compensation Plan, Value	(89)			(89)	860	(860)
Adjustments to Non-controlling Interest	0			(4)						4
Preferred Share distributions	(1,725)								(1,725)
Distributions declared ($0.45 per share)	(23,903)								(23,638)	(265)
Ending Balance at Mar. 31, 2014	1,895,152	40	1,567	2,974,094	6,267	(6,267)	520,322	(3,905)	(1,617,878)	20,912
Ending Balance, Shares at Mar. 31, 2014		4,000,000	156,916,901		384,571
Beginning Balance at Dec. 31, 2014	2,159,326	40	1,793	3,314,693	6,219	(6,219)	529,487	(4,607)	(1,700,579)	18,499
Beginning Balance, Shares at Dec. 31, 2014		4,000,000	179,293,160		384,536
Net income (loss)	8,594						8,536			58
Other comprehensive loss	(2,605)							(2,583)		(22)
Bonus Share Issuance, Shares			8,447
Bonus Share Issuance, Value	125			125
Equity Issuance Costs	(48)			(48)
Share Based Compensation Activity, Shares			410,506		280,011
Share Based Compensation Activity, Value	2,352		5	2,347
Share Issuance from/to Deferred Compensation Plan, Shares			33,485		30,144
Share issuance from/to Deferred Compensation Plan, Value	0				4,975	(4,975)
Adjustments to Non-controlling Interest	0			20						(20)
Preferred Share distributions	(1,725)								(1,725)
Distributions declared ($0.45 per share)	(27,443)								(27,213)	(230)
Ending Balance at Mar. 31, 2015	$ 2,138,576	$ 40	$ 1,798	$ 3,317,137	$ 11,194	$ (11,194)	$ 538,023	$ (7,190)	$ (1,729,517)	$ 18,285
Ending Balance, Shares at Mar. 31, 2015		4,000,000	179,745,598		694,691