Financial Instruments and Fair Value Measurements - Schedule of Derivative Financial Instruments (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Fair value, liability derivatives	$ (104,253)	$ (39,061)
Fair value, asset derivatives	14	2,583
Interest Rate Swaps
Derivatives, Fair Value [Line Items]
Aggregate Notional Amount	50,000
Core Portfolio
Derivatives, Fair Value [Line Items]
Aggregate Notional Amount	562,297
Fair value, derivatives, net	(85,461)	(33,294)
Core Portfolio \| Interest Rate Swaps \| Other Liabilities
Derivatives, Fair Value [Line Items]
Aggregate Notional Amount	562,297
Fair value, liability derivatives	(85,461)	(33,750)
Core Portfolio \| Interest Rate Swaps \| Other Assets
Derivatives, Fair Value [Line Items]
Aggregate Notional Amount	0
Fair value, asset derivatives	$ 0	456
Core Portfolio \| Interest Rate Swaps \| Minimum \| Other Liabilities
Derivatives, Fair Value [Line Items]
Derivative Effective Date	2012-12
Derivative Maturity Date	2022-07
Strike Rate	1.24%
Core Portfolio \| Interest Rate Swaps \| Maximum \| Other Liabilities
Derivatives, Fair Value [Line Items]
Derivative Effective Date	2023-04
Derivative Maturity Date	2033-04
Strike Rate	3.77%
Fund Portfolio \| Fund II
Derivatives, Fair Value [Line Items]
Aggregate Notional Amount	$ 64,007
Fair value, derivatives, net	(368)	(138)
Fund Portfolio \| Fund II \| Interest Rate Swaps \| Other Liabilities
Derivatives, Fair Value [Line Items]
Aggregate Notional Amount	$ 19,007
Derivative Effective Date	2014-10
Derivative Maturity Date	2021-11
Fair value, liability derivatives	$ (380)	(139)
Fund Portfolio \| Fund II \| Interest Rate Swaps \| Minimum \| Other Liabilities
Derivatives, Fair Value [Line Items]
Strike Rate	2.88%
Fund Portfolio \| Fund II \| Interest Rate Swaps \| Maximum \| Other Liabilities
Derivatives, Fair Value [Line Items]
Strike Rate	2.88%
Fund Portfolio \| Fund II \| Interest Rate Cap \| Other Assets
Derivatives, Fair Value [Line Items]
Aggregate Notional Amount	$ 45,000
Derivative Effective Date	2019-03
Derivative Maturity Date	2022-03
Fair value, asset derivatives	$ 12	1
Fund Portfolio \| Fund II \| Interest Rate Cap \| Minimum \| Other Assets
Derivatives, Fair Value [Line Items]
Strike Rate	3.50%
Fund Portfolio \| Fund II \| Interest Rate Cap \| Maximum \| Other Assets
Derivatives, Fair Value [Line Items]
Strike Rate	3.50%
Fund Portfolio \| Fund IV
Derivatives, Fair Value [Line Items]
Aggregate Notional Amount	$ 169,808
Fair value, derivatives, net	(2,780)	(790)
Fund Portfolio \| Fund IV \| Interest Rate Swaps \| Other Liabilities
Derivatives, Fair Value [Line Items]
Aggregate Notional Amount	79,208
Fair value, liability derivatives	(2,782)	(812)
Fund Portfolio \| Fund IV \| Interest Rate Swaps \| Other Assets
Derivatives, Fair Value [Line Items]
Aggregate Notional Amount	0
Fair value, asset derivatives	$ 0	22
Fund Portfolio \| Fund IV \| Interest Rate Swaps \| Minimum \| Other Liabilities
Derivatives, Fair Value [Line Items]
Derivative Effective Date	2017-03
Derivative Maturity Date	2022-04
Strike Rate	1.48%
Fund Portfolio \| Fund IV \| Interest Rate Swaps \| Maximum \| Other Liabilities
Derivatives, Fair Value [Line Items]
Derivative Effective Date	2019-12
Derivative Maturity Date	2022-12
Strike Rate	4.00%
Fund Portfolio \| Fund IV \| Interest Rate Cap \| Other Assets
Derivatives, Fair Value [Line Items]
Aggregate Notional Amount	$ 90,600
Fair value, asset derivatives	$ 2	0
Fund Portfolio \| Fund IV \| Interest Rate Cap \| Minimum \| Other Assets
Derivatives, Fair Value [Line Items]
Derivative Effective Date	2019-07
Derivative Maturity Date	2020-12
Strike Rate	3.00%
Fund Portfolio \| Fund IV \| Interest Rate Cap \| Maximum \| Other Assets
Derivatives, Fair Value [Line Items]
Derivative Effective Date	2019-12
Derivative Maturity Date	2021-07
Strike Rate	3.50%
Fund Portfolio \| Fund III \| Interest Rate Cap \| Other Assets
Derivatives, Fair Value [Line Items]
Aggregate Notional Amount	$ 39,470
Derivative Effective Date	2020-01
Derivative Maturity Date	2021-01
Fair value, asset derivatives	$ 0	0
Fund Portfolio \| Fund III \| Interest Rate Cap \| Minimum \| Other Assets
Derivatives, Fair Value [Line Items]
Strike Rate	3.00%
Fund Portfolio \| Fund III \| Interest Rate Cap \| Maximum \| Other Assets
Derivatives, Fair Value [Line Items]
Strike Rate	3.00%
Fund Portfolio \| Fund V
Derivatives, Fair Value [Line Items]
Aggregate Notional Amount	$ 334,593
Fair value, derivatives, net	(15,630)	(2,256)
Fund Portfolio \| Fund V \| Interest Rate Swaps \| Other Liabilities
Derivatives, Fair Value [Line Items]
Aggregate Notional Amount	334,593
Fair value, liability derivatives	(15,630)	(4,360)
Fund Portfolio \| Fund V \| Interest Rate Swaps \| Other Assets
Derivatives, Fair Value [Line Items]
Aggregate Notional Amount	0
Fair value, asset derivatives	$ 0	$ 2,104
Fund Portfolio \| Fund V \| Interest Rate Swaps \| Minimum \| Other Liabilities
Derivatives, Fair Value [Line Items]
Derivative Effective Date	2018-01
Derivative Maturity Date	2021-02
Strike Rate	1.25%
Fund Portfolio \| Fund V \| Interest Rate Swaps \| Maximum \| Other Liabilities
Derivatives, Fair Value [Line Items]
Derivative Effective Date	2019-11
Derivative Maturity Date	2024-10
Strike Rate	2.88%

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Derivative maturity month year.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

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- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Variable interest rate in effect as of the balance sheet date related to the interest rate derivative.

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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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No definition available.

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