Fair Values - Schedule of Details of Book Value, Face Amount, and Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Financial assets
Cash and cash equivalents	$ 80,584	$ 105,662
Loans receivable, net	14,372,950	14,293,970
Debt securities held-to-maturity	97,174	99,000
Financial liabilities
Secured debt agreements, net, face amount	8,283,613	8,996,481
Loan participations sold, net		94,418
Loan participations sold, net, face amount		123,745
Securitized debt obligations, net	1,287,364	1,285,471
Securitized debt obligations, net,face amount	1,292,120	1,292,120
Secured term loan, net	500,000
Book Value [Member]
Financial assets
Cash and cash equivalents	80,584	105,662
Loans receivable, net	14,280,919	14,191,200
Debt securities held-to-maturity	94,595	96,167
Financial liabilities
Secured debt agreements, net	8,257,370	8,974,756
Loan participations sold, net		94,418
Securitized debt obligations, net	1,287,364	1,285,471
Secured term loan, net	491,598
Convertible notes, net	611,472	609,911
Fair Value [Member]
Financial assets
Cash and cash equivalents	80,584	105,662
Loans receivable, net	14,375,273	14,294,836
Debt securities held-to-maturity	96,239	96,600
Financial liabilities
Secured debt agreements, net	8,283,613	8,996,481
Loan participations sold, net		94,528
Securitized debt obligations, net	1,291,784	1,283,086
Secured term loan, net	501,095
Convertible notes, net	649,275	605,348
Convertible Senior Note [Member]
Financial liabilities
Convertible notes, net, face amount	$ 622,500	622,500
Senior Participation [Member]
Financial liabilities
Loan participations sold, net		94,418
Loan participations sold, net, face amount		$ 94,528

Amount of investment in debt security measured at face amount (held-to-maturity).

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- Definition

Participating Mortgage Loans Participation Liabilities Principal Amount

+ References

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- Definition

Secured Debt Repurchase Agreements Gross

+ References

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- Definition

Securitized debt obligations net.

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Securitized debt obligations, net, face amount.

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- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

No definition available.

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- Definition

Fair value portion of borrowing which can be exchanged for a specified number of another security at the option of the issuer or the holder, for example, but not limited to, the entity's common stock.

+ References

No definition available.

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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

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- Definition

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

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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

The aggregate amount of the participation liability at the end of the accounting period.

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-Topic 470
-SubTopic 30
-Section 50
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- Definition

Carrying amount of collateralized debt obligations with maturities initially due after one year or beyond the operating cycle, if longer, excluding the current portion. Obligations include, but not limited to, mortgage loans, chattel loans, and other borrowings secured by assets.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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