Variable Interest Entities - Carrying Value for Residential Mortgage Loans (Detail) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Carrying value	[1]	$ 416,571	$ 458,348
Residential Mortgage Backed Securities
Variable Interest Entity [Line Items]
Principal balance		137,911	148,908
Unamortized premium and costs		3,790	4,014
Allowance for loan losses		(56)
Carrying value		141,645	152,922		$ 11,660
Variable Interest Entities Primary Beneficiary
Variable Interest Entity [Line Items]
Allowance for loan losses			(175,000)
Variable Interest Entities Primary Beneficiary | Residential Mortgage Backed Securities
Variable Interest Entity [Line Items]
Principal balance		415,320	456,768
Unamortized premium and costs		1,418	1,755
Allowance for loan losses		(167)	(175)	$ (175)	(186)
Carrying value		$ 416,571	$ 458,348		$ 549,016

[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 March 31, 2020 and December 31, 2019, total assets of the consolidated VIEs were $418 million and $460 million (including accrued interest receivable of $1.3 million and $1.5 million), respectively (which is recorded above in the line item entitled “Interest receivable”), and total liabilities were $409 million and $450 million (including accrued interest payable of $1.3 million and $1.4 million), respectively (which is recorded in the line item above entitled “Accrued interest payable”). Please refer to Note 5, “Variable Interest Entities,” for further discussion.See accompanying notes to unaudited consolidated financial statements.