Summary of Financial Instruments for Which Fair Value Option Has Been Elected (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Option, Quantitative Disclosures [Line Items]
Loans and Receivables	$ 187,831	$ 304,173
Assets	7,958,297	7,990,666
Liabilities	6,630,723	6,536,723
Debt Securities
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments	576,306	529,698
Equity and Preferred Securities
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments	223,630	390,095
Corporate Loans \| Assets Of Consolidated CLO Vehicles
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments	6,969,542	6,766,700
Other \| Assets Of Consolidated CLO Vehicles
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments	988
Liabilities of Consolidated CLO Vehicles \| Senior Secured Notes
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of Loan payable	6,474,210	6,473,233
Fair value of due to Affiliates	45,243	3,201
Liabilities of Consolidated CLO Vehicles \| Subordinated Notes
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of Loan payable	61,695	7,478
Fair value of due to Affiliates	$ 49,575	$ 52,811

Due to Affiliate Fair Value

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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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

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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- Definition

Fair value portion of contractual obligation to pay money on demand or on fixed or determinable dates.

+ References

No definition available.

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- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

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- Definition

Fair value portion of notes payable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19,20,22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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