Investments in real estate Schedule of investment in real estates (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Construction in progress ("CIP")/current value-added projects:
Real Estate Investment Property, at Cost	$ 9,200,568	$ 8,945,261
Land/future value-added projects:
Less: accumulated depreciation	(1,425,960)	(1,315,339)
Investments in real estate, net	7,774,608	7,629,922
North America
Real Estate Properties [Line Items]
Land (related to rental properties)	676,359	677,649
Buildings and building improvements	6,751,689	6,644,634
Other improvements	336,799	260,605
Rental properties	7,764,847	7,582,888
Construction in progress ("CIP")/current value-added projects:
Real Estate Investment Property, at Cost	9,124,007	8,707,533
Land/future value-added projects:
Land available for development	233,696	206,939
Asia
Construction in progress ("CIP")/current value-added projects:
Real Estate Investment Property, at Cost	76,561	237,728
Construction in progress ("CIP")/current value-added projects: \| North America
Construction in progress ("CIP")/current value-added projects:
Development in process	1,125,464	917,706
Current, Near-Term and Future Value-Creation Projects [Member] \| North America
Construction in progress ("CIP")/current value-added projects:
Real Estate Investment Property, at Cost	$ 1,359,160	$ 1,124,645

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Carrying amount as of the balance sheet date of improvements not otherwise specified in the existing taxonomy.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.10)
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-Publisher FASB
-Name Accounting Standards Codification
-Glossary Phase
-URI http://asc.fasb.org/extlink&oid=49177889

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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