Consolidated Statement Of Changes In Equity - USD ($) $ in Thousands	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]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total equity	$ 1,926,489	$ 589	$ 139	$ 2,283,440	$ (67,846)	$ 12,566	$ (302,776)	$ 377
Balance (in shares) at Dec. 31, 2014		58,952,404	13,850,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted share units issued to Trustees		18,036
Issuance of nonvested shares, net		206,185
Issuance of nonvested shares, net	(1,907)	$ (2)		(1,941)	36
Purchase of common shares for vesting	8,223				8,223
Amortization of nonvested shares	(3,154)			(3,154)
Share option expense	550			550
share based compensation included in retirement severance expense	6,377			6,377
Foreign currency translation adjustment	(14,912)					(14,912)
Change in unrealized gain/loss on derivatives	10,636					10,636
Net income	91,587						91,587
Issuances of common shares (in shares)		5,659
Issuances of common shares	$ 337	$ 0		337
Stock option exercises, net (in shares)	22,625	22,625
Stock option exercises, net	$ (34)	$ (1)		(1,104)	(1,139)
Dividends to common and preferred shareholders	(115,725)						(115,725)
Balance (in shares) at Jun. 30, 2015		59,204,909	13,850,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total equity	$ 1,902,143	$ 592	$ 139	$ 2,296,903	$ (77,244)	$ 8,290	$ (326,914)	$ 377