Consolidated Statements Of Equity And Comprehensive Income (USD $) In Thousands	Comprehensive Income (Loss) [Member]	Shares of Beneficial Interest, $1.00 Par [Member]	Capital Contributed in Excess of Par [Member]	Accumulated Other Comprehensive Loss [Member]	Distributions in Excess of Net Income [Member]	Non-controlling Interest [Member]	Total
Balance, at Dec. 31, 2010		$ 55,436	$ 1,040,023	$ (39,993)	$ (401,193)	$ 50,257	$ 704,530
Comprehensive income (loss):
Net loss	(33,930)				(32,566)	(1,364)	(33,930)
Unrealized gain on derivatives	1,775			1,704		71	1,775
Other comprehensive income	242			233		9	242
Total comprehensive loss	(31,913)					(1,284)	(31,913)
Shares issued under distribution reinvestment and share purchase plan		4	50				54
Shares issued under employee share purchase plan		18	244				262
Shares issued under equity incentive plans, net of retirements		228	(2,103)				(1,875)
Amortization of deferred compensation			4,626				4,626
Distributions paid to common shareholders ($0.30 per share)					(16,685)		(16,685)
Noncontrolling interests:
Distributions to Operating Partnership unitholders ($0.30 per unit)						(697)	(697)
Other distributions to noncontrolling interest, net						(252)	(252)
Balance, at Jun. 30, 2011		$ 55,686	$ 1,042,840	$ (38,056)	$ (450,444)	$ 48,024	$ 658,050