Investments in real estate Schedule of investment in real estates (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Real Estate Properties [Line Items]
Land (related to rental properties)	$ 678,752	$ 624,681
Buildings and building improvements	6,790,612	6,171,504
Other improvements	274,430	192,128
Rental properties	7,743,794	6,988,313
Land available for development	283,761	253,723
Gross investments in real estate	8,945,261	8,228,855
Less: accumulated depreciation	(1,315,339)	(1,120,245)
Investments in real estate	7,629,922	7,108,610
Construction in progress ("CIP")/current value-added projects:
Real Estate Properties [Line Items]
CIP/current value-creation projects	917,706	986,819
Current, Near-Term and Future Value-Creation Projects
Real Estate Properties [Line Items]
Gross investments in real estate	$ 1,201,467	$ 1,240,542

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

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- Definition

The current amount of expenditures for a real estate project that has not yet been completed.

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Aggregate of the carrying amounts as of the balance sheet date of investments in building and building improvements.

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Amount before accumulated depletion of real estate held for productive use, excluding land held for sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 4
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6812-107765

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-Publisher FASB
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.13)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Carrying amount of land available for development.

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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.(a),1(d))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Number 210
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The cumulative amount of depreciation for real estate property held for investment purposes.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 944
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Amount of real estate investment property which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Carrying amount of income producing properties held for rental.

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