Segment Reporting (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Segment Reporting Information Profit Loss [Abstract]
Revenues	$ 118,398,000	$ 70,001,000	$ 195,930,000	$ 132,266,000
Costs and Expenses	54,998,000	43,311,000	105,172,000	86,044,000
Interest Expense	5,396,000	3,765,000	9,836,000	7,476,000
Other, net	46,025,000	7,732,000	53,124,000	16,601,000
Benefit from (provision for) income taxes	24,760,000	6,751,000	32,334,000	10,863,000
Income (Loss) from Continuing Operations Attributable to Parent, Total	79,269,000	23,906,000	101,712,000	44,484,000
Segment Reporting Asset Balances [Abstract]
Total Long-Lived Assets	1,234,815,000		1,234,815,000		950,705,000
Total Assets	1,459,706,000		1,459,706,000		1,172,326,000
Revenues From International Investments [Line Items]
Lease Revenues	17,839,000	15,444,000	33,299,000	31,135,000
Income (Loss) from Equity Method Investments	12,465,000	7,638,000	18,681,000	16,780,000
Income from continuing operations before income taxes	103,646,000	30,946,000	133,936,000	55,525,000
Reimbursable Costs From Affiliates	17,100	14,800	34,800	29,400
Percentage Of Total Investment In Reit			23.00%
Asset Management [Member]
Segment Reporting Information Profit Loss [Abstract]
Revenues	94,850,000	49,761,000	151,614,000	92,559,000
Costs and Expenses	41,315,000	33,266,000	80,238,000	65,752,000
Other, net	4,510,000	1,846,000	7,226,000	2,889,000
Benefit from (provision for) income taxes	26,056,000	6,373,000	33,436,000	9,948,000
Income (Loss) from Continuing Operations Attributable to Parent, Total	31,989,000	11,968,000	45,166,000	19,748,000
Segment Reporting Asset Balances [Abstract]
Total Long-Lived Assets	3,088,000		3,088,000		3,729,000
Total Assets	120,001,000		120,001,000		123,921,000
Real Estate Investment [Member]
Segment Reporting Information Profit Loss [Abstract]
Revenues	23,548,000	20,240,000	44,316,000	39,707,000
Costs and Expenses	13,683,000	10,045,000	24,934,000	20,292,000
Interest Expense	5,396,000	3,765,000	9,836,000	7,476,000
Other, net	41,515,000	5,886,000	45,898,000	13,712,000
Benefit from (provision for) income taxes	(1,296,000)	378,000	(1,102,000)	915,000
Income (Loss) from Continuing Operations Attributable to Parent, Total	47,280,000	11,938,000	56,546,000	24,736,000
Segment Reporting Asset Balances [Abstract]
Total Long-Lived Assets	1,231,727,000		1,231,727,000		946,976,000
Total Assets	1,339,705,000		1,339,705,000		1,048,405,000
Segment Geographical Groups Of Countries Group One Member
Revenues From International Investments [Line Items]
Lease Revenues	2,134,000	1,450,000	4,132,000	2,836,000
Income (Loss) from Equity Method Investments	1,627,000	1,416,000	3,149,000	2,976,000
Income from continuing operations before income taxes	3,761,000	2,866,000	7,281,000	5,812,000
Total Long Lived Assets International	$ 74,239,000		$ 74,239,000		$ 69,126,000