CONDENSED CONSOLIDATED STATEMENT OF CHANGES IN EQUITY (Unaudited) (USD $) In Thousands	Total	Preferred Shares [Member]	Common Shares [Member]	Additional Paid-in-Capital [Member]	Accumulated Distributions in Excess of Net Income [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Non-controlling Interests [Member]
Balance at Dec. 31, 2010	$ 1,356,129	$ 327,867	$ 15	$ 1,937,942	$ (985,562)	$ (106)	$ 75,973
Redemption of noncontrolling OP units for common shares	0	0	0	343	0	0	(343)
Repurchase of preferred shares	(657)	(743)	0	0	86	0	0
Issuance of common shares and amortization of deferred compensation costs, net	2,831	0	0	2,831	0	0	0
Dividends/distributions	(24,642)	0	0	0	(23,120)	0	(1,522)
Net income (loss)	(15,993)	0	0	0	(17,439)	0	1,446
Other comprehensive income (loss)	632	0	0	0	0	632	0
Balance at Mar. 31, 2011	1,318,300	327,124	15	1,941,116	(1,026,035)	526	75,554
Balance at Dec. 31, 2011	1,221,431	311,673	15	2,010,850	(1,161,402)	1,938	58,357
Repurchase of preferred shares	(1,461)	(1,690)	0	0	229	0	0
Issuance of common shares and amortization of deferred compensation costs, net	3,119	0	1	3,118	0	0	0
Contributions from noncontrolling interests	889	0	0	0	0	0	889
Dividends/distributions	(26,494)	0	0	0	(25,276)	0	(1,218)
Net income (loss)	5,478	0	0	0	3,611	0	1,867
Other comprehensive income (loss)	(56)	0	0	0	0	(56)	0
Balance at Mar. 31, 2012	$ 1,202,906	$ 309,983	$ 16	$ 2,013,968	$ (1,182,838)	$ 1,882	$ 59,895