Secured Financings on Investments in Real Estate Debt - Summary of Secured Financings on Investments in Real Estate Debt (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Weighted Average Maturity Date	Jun. 29, 2025	Sep. 21, 2025
Collateral Assets	$ 3,568,742	$ 3,956,882
Outstanding Balance	$ 2,392,945	$ 3,092,137
Barclays MRA [Member]
Debt Instrument [Line Items]
Weighted Average Maturity Date	Sep. 29, 2021	Sep. 29, 2021
Security Interests	CMBS	CMBS
Collateral Assets	$ 1,160,359	$ 981,652
Outstanding Balance	$ 750,000	$ 750,000
Prepayment Provisions	None	None
RBC MRA [Member]
Debt Instrument [Line Items]
Weighted Average Maturity Date	Mar. 20, 2021	Jun. 23, 2020
Security Interests	CMBS/Corporate bonds	CMBS/Corporate bonds
Collateral Assets	$ 1,678,005	$ 1,980,951
Outstanding Balance	$ 1,172,595	$ 1,561,642
Prepayment Provisions	None	None
Citi MRA [Member]
Debt Instrument [Line Items]
Weighted Average Maturity Date	Mar. 30, 2021	Jan. 14, 2020
Security Interests	CMBS/RMBS	CMBS/Corporate bonds
Collateral Assets	$ 265,697	$ 266,406
Outstanding Balance	$ 170,412	$ 205,762
Prepayment Provisions	None	None
DB Secured Financing [Member]
Debt Instrument [Line Items]
Weighted Average Maturity Date	Apr. 02, 2022
Security Interests	Term Loan
Collateral Assets	$ 409,154
Outstanding Balance	$ 263,866
Prepayment Provisions	None
Citi Term Loan TRS [Member]
Debt Instrument [Line Items]
Weighted Average Maturity Date	Jul. 09, 2021
Security Interests	Term Loans
Collateral Assets	$ 55,527
Outstanding Balance	$ 36,072
Prepayment Provisions	None
MS MRA [Member]
Debt Instrument [Line Items]
Weighted Average Maturity Date		Feb. 01, 2020
Security Interests		CMBS
Collateral Assets		$ 636,734
Outstanding Balance		$ 508,510
Prepayment Provisions		None
MUFG MRA [Member]
Debt Instrument [Line Items]
Weighted Average Maturity Date		Apr. 30, 2020
Security Interests		CMBS
Collateral Assets		$ 86,332
Outstanding Balance		$ 62,561
Prepayment Provisions		None
BAML MRA [Member]
Debt Instrument [Line Items]
Weighted Average Maturity Date		Jan. 24, 2020
Security Interests		CMBS/Corporate bonds
Collateral Assets		$ 4,807
Outstanding Balance		$ 3,662
Prepayment Provisions		None

Debt instrument prepayment provisions.

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- Definition

Repurchase agreements, security interests.

+ References

No definition available.

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- Definition

Weighted average maturity date.

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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.

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No definition available.

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- Definition

The fair value, as of the date of each statement of financial position presented, of securities which are owned but transferred to serve as collateral for the payment of repurchase agreements, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

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- Definition

Carrying value, as of the balance sheet date, of securities sold under agreements to repurchase where the transferor maintains effective control over the assets, accounting for them as secured debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL34722452-111729

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(m)(1)(i))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

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