Mortgage Loans Held for Investment, Net and Related Non-Recourse Collateralized Financing (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Mortgage Loans Held for Investment, Net [Abstract]
Single-family mortgage loans held for investment, amortized cost	$ 15,885	$ 19,317
Seriously delinquent single-family mortgage loans	1,307	1,094
Allowance for credit losses	147	281
Provision for loan losses	$ 80	130	$ 180
Debt Instrument, Description of Variable Rate Basis	1-month LIBOR
Debt Instrument, Basis Spread on Variable Rate	0.30%
Debt Instrument, Maturity Date	Jan. 31, 2025
Pledged Financial Instruments, Not Separately Reported, Loans Receivable Pledged as Collateral	$ 6,233	7,200
Non-Recourse Debt	$ 5,596	$ 6,533

Mortgage Loans Held for Investment, Net [Abstract]

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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-Subparagraph (SX 210.5-02.22(a)(2))
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- Definition

This is the principal amount of loans (across all types of loans) that are overdue in payment by a set number of days.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

A valuation allowance for financing receivables that are expected to be uncollectible.

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- Definition

Amount before allowance of consumer real estate loans. Includes, but not limited to, construction financing, residential mortgage loans, and home equity lines of credit. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

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- Definition

The sum of the carrying amounts, as of the date of the latest financial statement presented, of loans receivable which are owned but transferred to serve as collateral for the payment of related debt obligations, primarily secured borrowings and repurchase agreements, and for which the transferees are not permitted to sell or re-pledge them to an unrelated party.

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- Definition

Amount of expense related to estimated loss from loan and lease transactions.

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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

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