CONDENSED CONSOLIDATED STATEMENT OF CHANGES IN EQUITY (Unaudited) (USD $) In Thousands, unless otherwise specified	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]
Beginning Balance at Dec. 31, 2012	$ 1,333,165	$ 243,790	$ 18	$ 2,212,949	$ (1,143,803)	$ (6,224)	$ 26,435
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of noncontrolling OP units for common shares	0	0	0	458	0	0	(458)
Issuance of common shares upon conversion of convertible notes	47,128	0	0	47,128	0	0	0
Issuance of common shares and deferred compensation amortization, net	300,130	0	3	300,127	0	0	0
Dividends/distributions	(37,448)	0	0	0	(36,546)	0	(902)
Net income (loss)	(2,123)	0	0	0	(2,620)	0	497
Other comprehensive loss	702	0	0	0	0	702	0
Ending Balance at Mar. 31, 2013	1,641,554	243,790	21	2,560,662	(1,182,969)	(5,522)	25,572
Beginning Balance at Dec. 31, 2013	1,539,483	94,016	23	2,717,787	(1,300,527)	4,439	23,745
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of noncontrolling OP units	(1,962)	0	0	(993)	0	0	(969)
Issuance of common shares upon conversion of convertible notes	3,149	0	0	3,149	0	0	0
Issuance of common shares and deferred compensation amortization, net	6,694	0	0	6,694	0	0	0
Dividends/distributions	(40,415)	0	0	0	(39,477)	0	(938)
Net income (loss)	1,814	0	0	0	886	0	928
Other comprehensive loss	(512)	0	0	0	0	(512)	0
Ending Balance at Mar. 31, 2014	$ 1,508,251	$ 94,016	$ 23	$ 2,726,637	$ (1,339,118)	$ 3,927	$ 22,766