Mortgage-Backed Securities - Geographical and Other Statistics (Detail) - Non-Agency RMBS [Member] $ in Thousands		Mar. 31, 2016 USD ($) Point	Dec. 31, 2015 USD ($) Point
Investment Holdings [Line Items]
Weighted average maturity		21 years 8 months 12 days	22 years
Weighted average amortized loan to value	[1]	67.60%	67.90%
Weighted average FICO | Point	[2]	671	671
Weighted average loan balance | $		$ 318	$ 330
Weighted average percentage owner occupied		82.70%	82.70%
Weighted average percentage single family residence		65.90%	65.90%
Weighted average current credit enhancement		2.40%	2.40%
California [Member]
Investment Holdings [Line Items]
Weighted average geographic concentration		30.60%	30.40%
Florida [Member]
Investment Holdings [Line Items]
Weighted average geographic concentration		8.10%	8.00%
New York [Member]
Investment Holdings [Line Items]
Weighted average geographic concentration		8.00%	8.00%
New Jersey [Member]
Investment Holdings [Line Items]
Weighted average geographic concentration		2.50%	2.50%

[1] Value represents appraised value of the collateral at the time of loan origination.

[2] FICO as determined at the time of loan origination.