Variable Interest Entities - Summary of Assets and Liabilities of Variable Interest Entities (Detail) - USD ($) $ in Thousands		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Variable Interest Entity [Line Items]
Residential mortgage loans held-for-investment through consolidated securitization trusts	[1]	$ 458,348		$ 549,016
Accrued interest receivable		16,398		16,872
Total Assets		4,938,631		5,039,700
Accrued interest payable		16,757		24,828
Asset-backed securities issued by securitization trusts	[1]	448,987		539,651
Total Liabilities		4,366,679		4,458,595
Residential Mortgage Backed Securities
Variable Interest Entity [Line Items]
Residential mortgage loans held-for-investment through consolidated securitization trusts		152,922		11,660
Variable Interest Entities Primary Beneficiary
Variable Interest Entity [Line Items]
Accrued interest receivable		1,500		1,800
Total Assets		460,000		551,000
Accrued interest payable		1,400		1,700
Asset-backed securities issued by securitization trusts		449,000		539,700
Total Liabilities		450,000		541,000
Variable Interest Entities Primary Beneficiary | Residential Mortgage Backed Securities
Variable Interest Entity [Line Items]
Residential mortgage loans held-for-investment through consolidated securitization trusts		458,348	[1]	549,016	[1]	$ 639,351
Accrued interest receivable		1,495		1,792
Total Assets		459,843		550,808
Accrued interest payable		1,448		1,746
Asset-backed securities issued by securitization trusts	[1]	448,987		539,651
Total Liabilities		$ 450,435		$ 541,397

[1] The consolidated balance sheets include assets of consolidated variable interest entities, or 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 December 31, 2019 and December 31, 2018, total assets of the consolidated VIEs were $460 million and $551 million (including accrued interest receivable of $1.5 million and $1.8 million), respectively (which is recorded above in the line item “Interest and dividends receivable”), and total liabilities were $450 million and $541 million (including accrued interest payable of $1.4 million and $1.7 million), respectively (which is recorded above in the line item “Accrued interest payable”). Please refer to Note 5, “Variable Interest Entities,” for further discussion.