Commitments, Contingencies and Guarantees - Schedule of Debt Related to Unconsolidated Funds (Details) $ in Thousands	3 Months Ended
Mar. 31, 2016 USD ($) property	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Long-term debt	$ 4,469,957	$ 3,611,276
Fund X [Member]
Debt Instrument [Line Items]
Long-term debt	$ 325,000
Loan Maturity Date	May 01, 2018
Debt Instrument, Collateral, Number of Properties \| property	6
Maximum future payments under the swap agreement	$ 2,100
Fund X [Member] \| Interest Rate Swap [Member]
Debt Instrument [Line Items]
Swap Fixed Interest Rate	2.35%
Partnership X [Member]
Debt Instrument [Line Items]
Long-term debt	$ 110,000
Loan Maturity Date	Mar. 01, 2023
Debt Instrument, Collateral, Number of Properties \| property	2
Maximum future payments under the swap agreement	$ 5,000
Partnership X [Member] \| Interest Rate Swap [Member]
Debt Instrument [Line Items]
Swap Fixed Interest Rate	2.30%
Unconsolidated Funds [Member]
Debt Instrument [Line Items]
Long-term debt	$ 435,000

Debt Instrument, Collateral, Number of Properties

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- Definition

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.

+ References

No definition available.

+ Details

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

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- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

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)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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