Real Estate - Summary of Dispositions (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014 Property sqft	Dec. 31, 2013 sqft Property	Dec. 31, 2012 sqft Property	Jun. 30, 2014 sqft
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties	1,278us-gaap_NumberOfRealEstateProperties	1,323us-gaap_NumberOfRealEstateProperties	1,157us-gaap_NumberOfRealEstateProperties
Square feet	260,700,000us-gaap_AreaOfRealEstateProperty	264,300,000us-gaap_AreaOfRealEstateProperty	208,800,000us-gaap_AreaOfRealEstateProperty	12,600,000us-gaap_AreaOfRealEstateProperty
Continuing Operations [Member] \| Contributions to Unconsolidated Co-investment Ventures [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties	126	254	25
Square feet	25,247,000	71,503,000	4,784,000
Net proceeds	$ 1,825,311	$ 6,479,707	$ 380,880
Net gains on contributions	188,268	555,196	1,958
Continuing Operations [Member] \| Dispositions to Third Parties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties	145
Square feet	19,856,000
Net proceeds	1,365,318	177,273	94,587
Net gains on contributions	336,203	7,673	17,314
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties		89	200
Square feet		9,196,000	27,169,000
Net proceeds		608,286	1,562,189
Net gains from dispositions, including related impairment charges and taxes		$ 116,550	$ 35,098

Area of a real estate property.

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- Definition

Amount of gain (loss), after tax expense or benefit and not previously recognized, resulting from the sale of a business component.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e957-107759

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760

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- Definition

The net gain (loss) resulting from sales and other disposals of real estate owned for investment purposes.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.14(d))

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 14

-Subparagraph d

-Article 9

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- Definition

The number of real estate properties owned as of the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

Cash received from the sale of real estate that is held for investment, that is, it is part of an investing activity during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585

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