Secured Debt Agreements - Summary of Key Terms of Revolving Repurchase Facilities (Parenthetical) (Detail) - Revolving Repurchase Facilities [Member]	9 Months Ended
	Sep. 30, 2015 ExtensionOptions
Line of Credit Facility [Line Items]
Facility mature date	Jan. 07, 2018
Bank of America [Member]
Line of Credit Facility [Line Items]
Maturity period	Includes two one-year extension options which may be exercised at our sole discretion.
Number of extension options	2
Term of maturity date	1 year
MetLife [Member]
Line of Credit Facility [Line Items]
Maturity period	Includes five one-year extension options which may be exercised at our sole discretion.
Number of extension options	5
Term of maturity date	1 year
Societe Generale [Member]
Line of Credit Facility [Line Items]
Maturity period	Includes a one-year extension option which, subject to certain provisions, may be exercised at our discretion.
Number of extension options	1
Term of maturity date	1 year