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	1,077	0	0	(1,077)
Repurchase of preferred shares	(657)	(743)	0	0	86	0	0
Issuance of common shares and deferred compensation amortization, net	96,703	0	1	96,702	0	0	0
Dividends/distributions	(50,671)	0	0	0	(47,441)	0	(3,230)
Net income (loss)	(72,950)	0	0	0	(61,697)	0	(11,253)
Other comprehensive income (loss)	776	0	0	0	0	776	0
Balance at Jun. 30, 2011	1,329,330	327,124	16	2,035,721	(1,094,614)	670	60,413
Balance at Dec. 31, 2011	1,221,431	311,673	15	2,010,850	(1,161,402)	1,938	58,357
Redemption of noncontrolling OP units for common shares	0	0	0	353	0	0	(353)
Repurchase of preferred shares	(70,000)	(67,883)	0	0	(2,117)	0	0
Issuance of common shares and deferred compensation amortization, net	6,361	0	1	6,360	0	0	0
Contributions from noncontrolling interests	889	0	0	0	0	0	889
Dividends/distributions	(83,698)	0	0	0	(50,164)	0	(33,534)
Net income (loss)	11,104	0	0	0	8,121	0	2,983
Other comprehensive income (loss)	(5,559)	0	0	0	0	(5,559)	0
Balance at Jun. 30, 2012	$ 1,080,528	$ 243,790	$ 16	$ 2,017,563	$ (1,205,562)	$ (3,621)	$ 28,342