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	$ 1,304,901	$ 327,867	$ 15	$ 1,937,942	$ (1,036,790)	$ (106)	$ 75,973
Redemption of noncontrolling OP units for common shares	0	0	0	1,876	0	0	(1,876)
Repurchase of preferred shares	(1,431)	(1,646)	0	0	215	0	0
Issuance of common shares and deferred compensation amortization, net	99,437	0	1	99,436	0	0	0
Dividends/distributions	(75,695)	0	0	0	(71,789)	0	(3,906)
Net income (loss)	(103,794)	0	0	0	(92,611)	0	(11,183)
Other comprehensive income (loss)	1,342	0	0	0	0	1,342	0
Balance at Sep. 30, 2011	1,224,760	326,221	16	2,039,254	(1,200,975)	1,236	59,008
Balance at Dec. 31, 2011	1,170,203	311,673	15	2,010,850	(1,212,630)	1,938	58,357
Redemption of noncontrolling OP units for common shares	0	0	0	1,099	0	0	(1,099)
Repurchase of preferred shares	(70,000)	(67,883)	0	0	(2,117)	0	0
Issuance of common shares and deferred compensation amortization, net	8,910	0	1	8,909	0	0	0
Contributions from noncontrolling interests	1,262	0	0	0	0	0	1,262
Deconsolidation of consolidated joint venture	(782)	0	0	0	0	0	(782)
Dividends/distributions	(112,500)	0	0	0	(78,082)	0	(34,418)
Net income (loss)	186,393	0	0	0	182,663	0	3,730
Other comprehensive income (loss)	(8,331)	0	0	0	0	(8,331)	0
Balance at Sep. 30, 2012	$ 1,175,155	$ 243,790	$ 16	$ 2,020,858	$ (1,110,166)	$ (6,393)	$ 27,050