Secured Debt Agreements - Summary of Key Terms of Revolving Repurchase Facilities (Detail) - Revolving Repurchase Facilities [Member]	9 Months Ended	12 Months Ended
Sep. 30, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Advance Rate	79.10%	78.80%
Wells Fargo [Member]
Line of Credit Facility [Line Items]
Guarantee	25.00%
Advance Rate	79.60%
Margin Call	Collateral marks only
Term/Maturity	Term matched
Wells Fargo [Member] \| LIBOR [Member]
Line of Credit Facility [Line Items]
Rate	1.77%
MetLife [Member]
Line of Credit Facility [Line Items]
Guarantee	50.00%
Advance Rate	78.80%
Margin Call	Collateral marks only
Term/Maturity	April 22, 2022
MetLife [Member] \| LIBOR [Member]
Line of Credit Facility [Line Items]
Rate	1.84%
Bank of America [Member]
Line of Credit Facility [Line Items]
Guarantee	50.00%
Advance Rate	79.30%
Margin Call	Collateral marks only
Term/Maturity	May 21, 2021
Bank of America [Member] \| LIBOR [Member]
Line of Credit Facility [Line Items]
Rate	1.67%
JP Morgan [Member]
Line of Credit Facility [Line Items]
Guarantee	50.00%
Advance Rate	78.80%
Margin Call	Collateral marks only
Term/Maturity	January 7, 2019
JP Morgan [Member] \| LIBOR [Member]
Line of Credit Facility [Line Items]
Rate	1.84%
Citibank [Member]
Line of Credit Facility [Line Items]
Guarantee	25.00%
Advance Rate	78.30%
Margin Call	Collateral marks only
Term/Maturity	Term matched
Citibank [Member] \| LIBOR [Member]
Line of Credit Facility [Line Items]
Rate	1.85%
Morgan Stanley [Member]
Line of Credit Facility [Line Items]
Guarantee	25.00%
Advance Rate	78.80%
Margin Call	Collateral marks only
Term/Maturity	March 1, 2019
Morgan Stanley [Member] \| LIBOR [Member]
Line of Credit Facility [Line Items]
Rate	2.35%
Societe Generale [Member]
Line of Credit Facility [Line Items]
Guarantee	25.00%
Advance Rate	80.00%
Margin Call	Collateral marks only
Term/Maturity	Term matched
Societe Generale [Member] \| LIBOR [Member]
Line of Credit Facility [Line Items]
Rate	1.71%

Debt Instrument Revolving Repurchase Facilities Advance Rate

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- Definition

Debt Instrument Revolving Repurchase Facilities Guarantee Rate

+ References

No definition available.

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- Definition

Debt Instrument Revolving Repurchase Facilities Margin Call Description

+ References

No definition available.

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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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- Definition

Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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