Commitments, Contingencies and Guarantees - Schedule of Debt Related to Unconsolidated Funds (Details) $ in Thousands	6 Months Ended
Jun. 30, 2019 USD ($) property	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Principal Balance	$ 4,304,913	$ 4,134,030
Partnership X
Debt Instrument [Line Items]
Loan Maturity Date	Mar. 01, 2023
Principal Balance	$ 110,000
Collateral, number of properties \| property	2
Maximum future payments under the swap agreement	$ 1,700
Partnership X \| Interest Rate Swap
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
Debt Instrument [Line Items]
Loan Maturity Date	Jul. 01, 2024
Principal Balance	$ 400,000
Collateral, number of properties \| property	6
Maximum future payments under the swap agreement	$ 21,800
Loan agreement, one month LIBOR maximum for interest rate cap requirement	3.56%
Loan agreement, number of consecutive days	14 days
Fund X \| Interest Rate Swap
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
Debt Instrument [Line Items]
Principal Balance	$ 510,000
LIBOR \| Partnership X
Debt Instrument [Line Items]
Loan agreement LIBOR floor	0.00%
LIBOR \| Fund X
Debt Instrument [Line Items]
Loan agreement LIBOR floor	0.00%

Debt Instrument, Collateral, Number of Properties

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

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

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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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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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- 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/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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The percentage points added to the reference rate to compute the variable rate on the interest rate derivative.

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Fixed interest rate related to the interest rate derivative.

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

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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.

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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/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
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