Summary of Financial Instruments for Which Fair Value Option Has Been Elected (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Loans and Receivables	$ 163,135	$ 239,659
Assets	7,186,737	12,649,547
Liabilities	5,830,973	11,339,206
Debt Securities
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Investments	489,950	418,061
Other
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Investments		458
Equity and Preferred Securities
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Investments	476,499	475,485
Corporate Loans \| Assets Of Consolidated CLO Vehicles
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Investments	6,057,153	10,825,759
Corporate Bonds \| Assets Of Consolidated CLO Vehicles
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Investments		690,125
Liabilities of Consolidated CLO Vehicles \| Senior Secured Notes
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Fair value of Loan payable	5,612,150	10,594,656
Fair value of due to Affiliates	3,269	996
Liabilities of Consolidated CLO Vehicles \| Subordinated Notes
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Fair value of Loan payable	150,220	703,164
Fair value of due to Affiliates	$ 65,334	$ 40,390

Due to Affiliate Fair Value

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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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
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+ References

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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/presentationRef
-Publisher FASB
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Fair value of financial and nonfinancial obligations.

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

+ References

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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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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