Secured Borrowings (Details)	1 Months Ended
Oct. 31, 2017 fund	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Schedule of Capitalization, Long-term Debt [Line Items]
Number of legacy funds included in sale of Certificates \| fund	6
Legacy funds transferred that did not meet the definition of participating interests \| fund	2
Secured borrowings - amount originally sold to investor		$ 179,300,000	$ 232,400,000.0
Fair value of credit support agreement		(2,700,000)	(2,800,000)
Secured Borrowings \| Loans Held for Investment
Schedule of Capitalization, Long-term Debt [Line Items]
Loans pledged as collateral		$ 187,000,000	$ 242,700,000

Credit Support Agreement, Fair Value

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- Definition

Legacy Funds with Participations Sold that were not Participating Interests by Definition

+ References

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- Definition

Number of Legacy Funds Included in Sale of Certificates

+ References

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- Definition

Carrying amount as of the balance sheet date of loans that have been pledged as collateral for borrowings. If the secured party has the right by contract or custom to sell or re-pledge the collateral, then the debtor reclassifies that asset and report that asset in its statement of financial position separately from other assets not so encumbered.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5086-111524

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+ References

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- Definition

Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-Section S99
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-Subparagraph (SX 210.7-03(a)(16))
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