Commitments, Contingencies and Guarantees - Schedule of Debt Related to Unconsolidated Funds (Details) $ in Thousands	9 Months Ended
Sep. 30, 2017 USD ($) property	Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Long-term debt	$ 4,048,828	$ 4,369,537
Partnership X [Member]
Debt Instrument [Line Items]
Loan Maturity Date	Mar. 01, 2023
Long-term debt	$ 110,000
Collateral, number of properties \| property	2
Maximum future payments under the swap agreement	$ 3,400
Partnership X [Member] \| Interest Rate Swap [Member]
Debt Instrument [Line Items]
Variable Interest Rate - basis spread	1.40%
Swap Fixed Interest Rate	2.30%
Swap Maturity Date	Mar. 01, 2021
Fund X [Member]
Debt Instrument [Line Items]
Loan Maturity Date	Jul. 01, 2024
Long-term debt	$ 400,000
Collateral, number of properties \| property	6
Maximum future payments under the swap agreement	$ 34,500
Loan agreement, one month LIBOR maximum for interest rate cap requirement	3.56%
Loan agreement, number of consecutive days	14 days
Fund X [Member] \| Interest Rate Swap [Member]
Debt Instrument [Line Items]
Variable Interest Rate - basis spread	1.65%
Swap Fixed Interest Rate	3.44%
Swap Maturity Date	Jul. 01, 2022
Unconsolidated Funds [Member]
Debt Instrument [Line Items]
Long-term debt	$ 510,000
LIBOR [Member] \| Partnership X [Member]
Debt Instrument [Line Items]
Loan agreement LIBOR floor	0.00%
LIBOR [Member] \| Fund X [Member]
Debt Instrument [Line Items]
Loan agreement LIBOR floor	0.00%

Debt Instrument, Collateral, Number of Properties

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- Definition

Debt Instrument, Maximum One Month LIBOR Trigger To Purchase Interest Rate Cap, Number Of Consecutive Days

+ References

No definition available.

+ Details

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- Definition

Debt Instrument, Maximum One Month LIBOR Trigger To Purchase Interest Rate Cap, Percent

+ References

No definition available.

+ Details

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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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.

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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

The percentage points added to the reference rate to compute the variable rate on the interest rate derivative.

+ References

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- Definition

Fixed interest rate related to the interest rate derivative.

+ References

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- Definition

Date the derivative contract matures, in CCYY-MM-DD format.

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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=82913245&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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