Loans at Fair Value - Summary of Distribution of Company's Loans at Fair Value (Detail) - USD ($) $ in Thousands		Sep. 30, 2024	Dec. 31, 2023
Financing Receivable Recorded Investment [Line Items]
Fair value		$ 1,429,525	$ 1,433,820
Asset-backed financings at fair value (1)	[1]	1,427,575	1,431,689
Loans at fair value, pledged to creditors		1,427,722	1,431,896
Loans in VIEs [Member]
Financing Receivable Recorded Investment [Line Items]
Fair value		1,427,575	1,431,689
Distressed [Member]
Financing Receivable Recorded Investment [Line Items]
Fair value		1,950	2,131
Agency-conforming loans secured by investment properties [Member]
Financing Receivable Recorded Investment [Line Items]
Fair value		1,379,963	1,383,392
Fixed interest rate jumbo loans held in a VIE [Member]
Financing Receivable Recorded Investment [Line Items]
Fair value		47,612	48,297
Loans acquired for sale at fair value [Member]
Financing Receivable Recorded Investment [Line Items]
Fair value		1,665,796	669,018
Assets sold under agreements to repurchase		$ 147	$ 207

[1] As discussed in Note 6 ‒ Variable Interest Entities ‒ Subordinate Mortgage-Backed Securities, the Company holds a portion of the securities issued by the VIEs. At September 30, 2024 and December 31, 2023, $83.4 million and $85.3 million, respectively, of such retained securities were pledged to secure Assets sold under agreements to repurchase.