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	861	0	0	(861)
Repurchase of preferred shares	(155,004)	(149,774)	0	0	(5,230)	0	0
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	307,263	0	3	307,260	0	0	0
Dividends/distributions	(72,850)	0	0	0	(70,872)	0	(1,978)
Net income	5,709	0	0	0	4,112	0	1,597
Other comprehensive loss	10,136	0	0	0	0	10,136	0
Ending Balance at Jun. 30, 2013	1,475,547	94,016	21	2,568,198	(1,215,793)	3,912	25,193
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	(959)	0	0	(1,003)
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	15,197	0	0	15,197	0	0	0
Dividends/distributions	(82,402)	0	0	0	(80,216)	0	(2,186)
Net income	17,101	0	0	0	15,336	0	1,765
Other comprehensive loss	(4,505)	0	0	0	0	(4,505)	0
Ending Balance at Jun. 30, 2014	$ 1,486,061	$ 94,016	$ 23	$ 2,735,174	$ (1,365,407)	$ (66)	$ 22,321