Consolidated Statement Of Changes In Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Preferred Stock [Member]	Additional paid-in capital [Member]	Treasury shares [Member]	Accumulated other comprehensive income (loss) [Member]	Distributions in excess of net income [Member]	Noncontrolling Interests [Member]	Series F Preferred Stock [Member]	Series F Preferred Stock [Member] Preferred Stock [Member]	Series F Preferred Stock [Member] Additional paid-in capital [Member]	Restricted Stock [Member]	Restricted Stock [Member] Additional paid-in capital [Member]	Employee Stock Option [Member]	Employee Stock Option [Member] Additional paid-in capital [Member]
Balance at Dec. 31, 2010	$ 1,631,258	$ 477	$ 167	$ 1,785,371	$ (39,762)	$ 38,842	$ (181,856)	$ 28,019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted share units issued to Trustees (in shares)		10,519
Restricted share units issued to Trustees	502			502
Issuance of nonvested shares, net		137,020
Issuance of nonvested shares, net	(1,102)	1		1,967	(3,070)
Amortization of share based comp												4,239	4,239	(778)	(778)
Foreign currency translation adjustment	1,651					1,651
Change in unrealized gain/loss on derivatives	1,620					1,620
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment Realized upon Sale or Liquidation, Net of Tax	(23,236)					(23,236)
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax						(4,586)
Net income	115,266						115,228	38
Issuances of common shares (in shares)		10,436
Issuances of common shares, net of costs	472	1		471
Redemption of preferred shares (in shares)			(3,200,000)
Redemption of preferred shares	(80,030)		(32)	(77,229)			(2,769)
Stock option exercises, net (in shares)	135,196	135,196
Stock option exercises, net	966	1		2,967	(2,002)
Dividends to common and preferred shareholders	(158,864)						(158,864)
Contributions from noncontrolling interests	(3)							(3)
Balance at Dec. 31, 2011	1,498,103	480	135	1,719,066	(44,834)	23,463	(228,261)	28,054
Balance (in shares) at Dec. 31, 2011		48,062,593	13,450,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted share units issued to Trustees (in shares)		10,925
Restricted share units issued to Trustees	488			488
Issuance of nonvested shares, net		148,095
Issuance of nonvested shares, net	(1,745)	1		1,491	(3,237)
Amortization of share based comp												4,402	4,402	(937)	(937)
Foreign currency translation adjustment	3,132					3,132
Change in unrealized gain/loss on derivatives	(5,973)					(5,973)
Net income	121,664						121,556	108
Issuances of common shares (in shares)		8,387								5,000,000
Issuances of common shares, net of costs	373	1		372					120,567	50	120,517
Redemption of preferred shares (in shares)			(4,600,000)
Redemption of preferred shares	(115,013)		(46)	(111,079)			(3,888)
Stock option exercises, net (in shares)	224,181	224,181
Stock option exercises, net	(1,987)	2		5,248	(7,237)
Dividends to common and preferred shareholders	(165,050)						(165,050)
Purchase of subsidiary shares from noncontrolling interest	0			27,785				27,785
Balance at Dec. 31, 2012	1,459,898	484	139	1,769,227	(55,308)	20,622	(275,643)	377
Balance (in shares) at Dec. 31, 2012		48,454,181	13,850,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted share units issued to Trustees (in shares)		17,530
Restricted share units issued to Trustees	(1,024)			1,024
Issuance of nonvested shares, net		196,928
Issuance of nonvested shares, net	(835)	2		2,588	(3,425)
Amortization of share based comp												4,832	4,832	(856)	(856)
Foreign currency translation adjustment	(13,049)					(13,049)
Change in unrealized gain/loss on derivatives	9,620					9,620
Net income	180,226						180,226
Issuances of common shares (in shares)		4,549,350
Issuances of common shares, net of costs	220,993	46		220,947
Stock option exercises, net (in shares)	143,272	143,272
Stock option exercises, net	947	2		4,389	(3,444)
Dividends to common and preferred shareholders	(176,498)						(176,498)
Balance at Dec. 31, 2013	$ 1,688,014	$ 534	$ 139	$ 2,003,863	$ (62,177)	$ 17,193	$ (271,915)	$ 377
Balance (in shares) at Dec. 31, 2013		53,361,261	13,850,000