CONSOLIDATED STATEMENT OF CHANGES IN EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Preferred Shares [Member]	Common Stock [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
Balance (in shares) at Dec. 31, 2010		11,455,200	146,552,589
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of noncontrolling OP units for common shares				2,187			(2,187)
Redemption of noncontrolling OP units for common shares (in shares)			398,927
Repurchase of common shares	(31,916)			(31,916)
Repurchase of common shares (in shares)			(3,974,645)
Repurchase of preferred shares	(15,456)	(16,194)			738
Repurchase of preferred shares (in shares)		(544,126)
Contributions from noncontrolling interests	2						2
Exercise of employee common share options, net	(221)			(221)
Exercise of employee common share options, net (in shares)			250,355
Obtained control of noncontrolling investment	574						574
Forfeiture of employee performance common shares	69				69
Forfeiture of employee performance common shares (in shares)			(10,140)
Issuance of common shares and deferred compensation amortization, net	102,416			102,416
Issuance of common shares and deferred compensation amortization, net (in shares)			11,721,265
Dividends/distributions	(102,874)				(97,063)		(5,811)
Comprehensive income (loss):
Net income (loss)	(89,778)				(79,584)		(10,194)
Other comprehensive income:
Other comprehensive income	2,044					2,044
Balance at Dec. 31, 2011	1,170,203	311,673	15	2,010,850	(1,212,630)	1,938	58,357
Balance (in shares) at Dec. 31, 2011		10,911,074	154,938,351
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of noncontrolling OP units for common shares				1,343			(1,343)
Redemption of noncontrolling OP units for common shares (in shares)			257,427
Repurchase of preferred shares	(70,000)	(67,883)			(2,117)
Repurchase of preferred shares (in shares)		(2,775,674)
Contributions from noncontrolling interests	1,262						1,262
Issuance of common shares upon conversion of Convertible Notes	33,770		1	33,769
Issuance of common shares upon conversion of convertible notes (in shares)	4,487,060		4,487,060
Exercise of employee common share options, net	(534)			(534)
Exercise of employee common share options, net (in shares)			110,944
Issuance of common shares and deferred compensation amortization, net	167,523		2	167,521
Issuance of common shares and deferred compensation amortization, net (in shares)			18,822,882
Deconsolidation of consolidated joint venture	(782)						(782)
Dividends/distributions	(144,753)				(109,372)		(35,381)
Comprehensive income (loss):
Net income (loss)	184,638				180,316		4,322
Other comprehensive income:
Other comprehensive income	(8,162)					(8,162)
Balance at Dec. 31, 2012	1,333,165	243,790	18	2,212,949	(1,143,803)	(6,224)	26,435
Balance (in shares) at Dec. 31, 2012		8,135,400	178,616,664
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of noncontrolling OP units for common shares				1,053			(1,053)
Redemption of noncontrolling OP units for common shares (in shares)			202,241
Repurchase of preferred shares	(155,004)	(149,774)			(5,230)
Acquisition of consolidated joint venture partners' equity interest	(8,918)				(8,918)
Repurchase of preferred shares (in shares)		(6,200,000)
Issuance of common shares upon conversion of Convertible Notes	60,686		1	60,685
Issuance of common shares upon conversion of convertible notes (in shares)	7,944,673		7,944,673
Exercise of employee common share options, net	(2,289)			(2,289)
Exercise of employee common share options, net (in shares)			955,478
Forfeiture of employee common shares	(20)			(20)
Forfeiture of employee common shares (in shares)			(3,571)
Issuance of common shares and deferred compensation amortization, net	440,835		4	440,831
Issuance of common shares and deferred compensation amortization, net (in shares)			40,947,537
Dividends/distributions	(148,076)				(144,206)		(3,870)
Comprehensive income (loss):
Net income (loss)	3,863				1,630		2,233
Other comprehensive income:
Other comprehensive income	10,663					10,663
Balance at Dec. 31, 2013	$ 1,539,483	$ 94,016	$ 23	$ 2,717,787	$ (1,300,527)	$ 4,439	$ 23,745
Balance (in shares) at Dec. 31, 2013		1,935,400	228,663,022