Secured Debt Agreements - Summary of Key Terms of Revolving Repurchase Facilities (Parenthetical) (Detail)	6 Months Ended
	Jun. 30, 2016 ExtensionOptions
Line of Credit Facility [Line Items]
Term of maturity date	6 months
Revolving Repurchase Facilities [Member] | 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
Revolving Repurchase Facilities [Member] | 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