Consolidated Statements of Changes in Equity (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	Total	Preferred Stock [Member]	Common Stock [Member]	Paid - in Capital	Distributions in Excess of Net Income	Accumulated Other Comprehensive Income/(Loss)	Non-controlling interest
Beginning Balance at Dec. 31, 2012	$ 2,993,832	$ 46,571	$ 2,501	$ 4,098,882	$ (1,143,781)	$ (11,257)	$ 916
Beginning Balance, Shares at Dec. 31, 2012		2,803,812	250,139,408
Consolidted Statements of Changes in Equity
Net income	4,924
Net income attributable to non-controlling interests	7						7
Other comprehensive loss	3,446					3,446
Issuance of common and restricted shares, Shares			(531,076)
Issuance of common and restricted shares	3,613		5	3,608
Adjustment for conversion of non-controlling interest of unitholders in Operating Partnership, Shares			71,841
Adjustment for conversion of non-controlling interest of unitholders in Operating Partnership	1,711		1	1,710
Common stock distributions declared ($0.235 per share)	(117,974)				(117,974)
Preferred stock distributions declared-Series E ($0.3322 per share)	(1,862)				(1,862)
Adjustment to reflect redemption value of redeemable non-controlling interests	(20,402)				(20,402)
Ending Balance at Jun. 30, 2013	$ 2,867,295	$ 46,571	$ 2,507	$ 4,104,200	$ (1,279,095)	$ (7,811)	$ 923
Ending Balance, Shares at Jun. 30, 2013		2,803,812	250,742,325