Dispositions (Details) (USD $)	1 Months Ended		3 Months Ended		12 Months Ended			1 Months Ended	3 Months Ended	12 Months Ended	1 Months Ended
	Jun. 30, 2011	Feb. 28, 2009	Dec. 31, 2010 sqft Property	Mar. 31, 2009	Dec. 31, 2011 Property sqft	Dec. 31, 2010	Dec. 31, 2009	Feb. 28, 2009 Japan [Member]	Mar. 31, 2009 Japan [Member]	Dec. 31, 2011 Japan [Member]	Feb. 28, 2009 China [Member]	Dec. 31, 2010 Shopping centers [Member] Property	Dec. 31, 2010 Office Building [Member] Property	Dec. 31, 2010 Mixed Use Projects [Member] Property	Dec. 31, 2010 Residential development joint ventures [Member] Property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties to be sold												4	2	11	2
Real estate property disposed (in square feet)			23,000,000		10,700,000
Total cash consideration		$ 1,300,000,000						$ 500,000,000			$ 845,500,000
Gain recognized on disposition of investment				(3,300,000)					(180,200,000)
Income tax expense related to the transaction										20,500,000
Dispositions (Textual) [Abstract]
Number of real estate properties disposed			182		94
Gross proceeds from selling of a portfolio	1,000,000,000		1,020,000,000		1,100,000,000
Net gain achieved			203,100,000		68,100,000
Loss from continuing operations			66,100,000		9,500,000
Gain from discontinued operations			269,200,000		58,600,000
Percentage of ownership interest			20.00%			20.00%
Impairment charge			168,800,000			168,800,000
Gains recognized on property acquisitions and dispositions, net					(111,684,000)	(28,488,000)	(35,262,000)
Resulting gain after completion of transaction						$ 4,400,000