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
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	1,083			1,083	0	0	0	0
Share option expense	256			256	0	0	0	0
Foreign currency translation adjustment	2,786			0	0	2,786	0	0
Change in unrealized gain/loss on derivatives	(2,488)			0	0	(2,488)	0	0
Net income	21,390			0	0	0	21,372	18
Purchase of 73,411 common shares for treasury	(3,209)			0	(3,209)	0	0	0
Issuances of common shares (in shares)		1,948	0
Issuances of common shares	85	0	0	85	0	0	0	0
Stock option exercises, net (in shares)	49,597	49,597	0
Stock option exercises, net	(480)	(1)	0	(925)	(1,406)	0	0	0
Dividends to common and preferred shareholders	(41,118)			0	0	0	(41,118)	0
Balance at Mar. 31, 2012	$ 1,477,895	$ 482	$ 135	$ 1,722,906	$ (49,454)	$ 23,761	$ (248,007)	$ 28,072
Balance (in shares) at Mar. 31, 2012		48,262,233	13,450,000