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]
Balance at Dec. 31, 2011	$ 1,498,103
Other Changes During Period Shares		10,925	0
Stockholders' Equity, Other	(488)	0	0	(488)	0	0	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of nonvested shares, including nonvested shares issued for the payment of bonuses (in shares)		148,095	0
Issuance of nonvested shares, including nonvested shares issued for the payment of bonuses	1,487	1	0	1,486	0	0	0	0
Cancellation of 185 employee nonvested shares	0			5	(5)
Amortization of nonvested shares	3,334			3,334	0	0	0	0
Share option expense	709			709	0	0	0	0
Foreign currency translation adjustment	4,855			0	0	4,855	0	0
Change in unrealized gain/loss on derivatives	(7,689)			0	0	(7,689)	0	0
Net income	92,383			0	0	0	92,322	61
Purchase of 73,959 common shares for treasury	(3,232)			0	(3,232)	0	0	0
Issuances of common shares (in shares)		6,317	0
Issuances of common shares	280	0	0	280	0	0	0	0
Stock option exercises, net (in shares)	58,543	58,543	0
Stock option exercises, net	(485)	(1)	0	(1,132)	(1,618)	0	0	0
Dividends to common and preferred shareholders	(123,379)			0	0	0	(123,379)	0
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	0			27,785				27,785
Balance at Sep. 30, 2012	$ 1,466,854	$ 482	$ 135	$ 1,754,285	$ (49,689)	$ 20,629	$ (259,318)	$ 330
Balance (in shares) at Sep. 30, 2012		48,286,473	13,450,000