Investments in real estate, net Schedule of investment in real estates (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Real Estate Properties [Line Items]
Land	$ 676,459	$ 624,681
Investment Building and Building Improvements	6,764,292	6,171,504
Improvements Others	250,364	192,128
Rental properties	7,691,115	6,988,313
Construction in progress ("CIP")/current value-added projects:
Real Estate Investment Property, at Cost	8,787,478	8,228,855
Land/future value-added projects:
Land available for development	311,932	683,101
Equity Method Investments	126,471	117,406
Real Estate Investments Property, including Unconsolidated Joint Ventures, at Cost	8,913,949	8,346,261
Less: accumulated depreciation	(1,259,740)	(1,120,245)
Investments in real estate, net	7,654,209	7,226,016
Construction in progress ("CIP")/current value-added projects:
Construction in progress ("CIP")/current value-added projects:
Development in process	784,431	557,441
Active development in North America \| North America [Member]
Construction in progress ("CIP")/current value-added projects:
Development in process	644,500	500,894
Active redevelopment in North America \| North America [Member]
Construction in progress ("CIP")/current value-added projects:
Development in process	139,931	42,482
Active development and redevelopment in Asia \| Asia [Member]
Construction in progress ("CIP")/current value-added projects:
Development in process	0	14,065
Current, Near-Term and Future Value-Creation Projects [Member]
Construction in progress ("CIP")/current value-added projects:
Real Estate Investment Property, at Cost	8,475,546	7,545,754
Land undergoing predevelopment activities (CIP) in North America (2) \| North America [Member]
Land/future value-added projects:
Land available for development	47,358	429,378
Land held for future development in North America
Land/future value-added projects:
Land available for development	264,574	253,723
Land held for future development in North America \| North America [Member]
Land/future value-added projects:
Land available for development	187,313	175,175
Land held for future development in North America \| Asia [Member]
Land/future value-added projects:
Land available for development	77,261	78,548
Current, Near-Term and Future Value-Creation Projects [Member]
Construction in progress ("CIP")/current value-added projects:
Real Estate Investment Property, at Cost	1,096,363	1,240,542
50, 60, and 100 Binney Street Project [Member] \| Land undergoing predevelopment activities (CIP) in North America (2) \| North America [Member]
Land/future value-added projects:
Land available for development	0	321,907
Other Projects in North America [Member] \| Land undergoing predevelopment activities (CIP) in North America (2) \| North America [Member]
Land/future value-added projects:
Land available for development	$ 47,358	$ 107,471

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