Variable Interest Entities - Summary of Assets and Liabilities of Variable Interest Entities (Detail) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Residential mortgage loans held-for-investment	[1]	$ 695,255	$ 744,462
Accrued interest receivable		16,864	16,203
Accrued interest payable		11,516	11,850
Asset-backed securities issued by securitization trusts	[1]	685,888	728,683
Variable Interest Entities Primary Beneficiary
Variable Interest Entity [Line Items]
Accrued interest receivable		2,300	2,500
Accrued interest payable		2,200	2,400
Asset-backed securities issued by securitization trusts		685,900	728,700
Variable Interest Entities Primary Beneficiary | Residential Mortgage Backed Securities
Variable Interest Entity [Line Items]
Residential mortgage loans held-for-investment		695,255	744,462
Accrued interest receivable		2,291	2,468
Total assets		697,546	746,930
Accrued interest payable		2,244	2,399
Asset-backed securities issued by securitization trusts		685,888	728,683
Total liabilities		$ 688,132	$ 731,082

[1] The consolidated balance sheets include assets of consolidated variable interest entities (“VIEs”) that can only be used to settle obligations and liabilities of the VIEs for which creditors do not have recourse to the Company. At June 30, 2017 and December 31, 2016, total assets of the consolidated VIEs were $698 million and $747 million (including accrued interest receivable of $2.3 million and $2.5 million), respectively, and total liabilities were $688 million and $731 million (including accrued interest payable of $2.2 million and $2.4 million), respectively. Please refer to Note 4, “Variable Interest Entities,” for further discussion.