Loans Held for Investment - Collateral Characteristics (Detail) - Loans Held for Investment at Fair Value - Seasoned Subprime Residential Mortgage Loans $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2018 USD ($) loan	Dec. 31, 2017 USD ($) loan
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Number of loans \| loan	144,451	149,172
Weighted average maturity (years)	18 years 9 months 24 days	18 years 9 months 18 days
Weighted average loan to value	87.50%	88.00%
Weighted average FICO	630	631
Weighted average loan balance (in thousands) \| $	$ 91	$ 91
Weighted average percentage owner occupied	92.80%	95.00%
Weighted average percentage single family residence	86.20%	86.00%
CA
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Weighted average geographic concentration of top four states	9.10%	9.00%
FL
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Weighted average geographic concentration of top four states	7.20%	7.20%
OH
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Weighted average geographic concentration of top four states	6.00%	6.10%
NY
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Weighted average geographic concentration of top four states	5.60%
PA
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Weighted average geographic concentration of top four states	5.60%	5.60%
VA
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Weighted average geographic concentration of top four states		5.50%

Indicates the number of mortgages under each classification.

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- Definition

Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]

+ References

No definition available.

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- Definition

The weighted average maturity period of underlying mortgages, which is based on their current face amounts.

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No definition available.

+ Details

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- Definition

As of the balance sheet date, the weighted average of underlying mortgages at amortized cost to their fair values determined using defined pricing methodologies.

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No definition available.

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- Definition

As of the balance sheet date, the weighted average credit score of underlying mortgages based on their FICO ratings.

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No definition available.

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- Definition

As of the balance sheet date, the percentage of unpaid principal amount of underlying mortgages originated in a specified territory.

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No definition available.

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- Definition

As of the balance sheet date, the weighted average of unpaid principal amounts of underlying mortgages.

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No definition available.

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- Definition

As of the balance sheet date, the weighted average of underlying mortgages that are owner occupied.

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No definition available.

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- Definition

As of the balance sheet date, the weighted average of underlying mortgages that are single family residences.

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No definition available.

+ Details

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