Loans Held for Investment - Key Characteristics of Residential Loan Portfolio (Details) - Loans Held for Investment at Fair Value - Seasoned Subprime Residential Mortgage Loans $ in Thousands	Jun. 30, 2023 USD ($) loan	Dec. 31, 2022 USD ($) loan
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Number of loans | loan	118,807	116,876
Weighted average maturity (years)	21 years 2 months 12 days	20 years 10 months 24 days
Weighted average loan to value	79.00%	82.20%
Weighted average FICO	665	658
Weighted average loan balance (in thousands) | $	$ 106	$ 103
Weighted average percentage owner-occupied	85.70%	87.50%
Weighted average percentage single family residence	78.30%	79.30%
CA
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Weighted average geographic concentration of top five states	14.70%	14.60%
FL
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Weighted average geographic concentration of top five states	8.90%	8.50%
NY
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Weighted average geographic concentration of top five states	8.40%	8.50%
PA
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Weighted average geographic concentration of top five states	4.50%	4.40%
VA
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Weighted average geographic concentration of top five states	4.30%	4.50%