Loans Held for Investment - Percentage of Securitized Loans Held For Investment Carried at Fair Value by Year Originated (Details) - Seasoned Subprime Residential Mortgage Loans - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Underlying mortgages excluded from portfolio		$ 152
Loans held for investment, at fair value
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Percentage of underlying mortgages, year originated	100.00%	100.00%
Loans held for investment, at fair value | 2002 and prior
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Percentage of underlying mortgages, year originated	5.00%	5.50%
Loans held for investment, at fair value | 2003
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Percentage of underlying mortgages, year originated	4.50%	4.80%
Loans held for investment, at fair value | 2004
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Percentage of underlying mortgages, year originated	8.30%	9.00%
Loans held for investment, at fair value | 2005
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Percentage of underlying mortgages, year originated	14.30%	15.30%
Loans held for investment, at fair value | 2006
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Percentage of underlying mortgages, year originated	18.10%	19.20%
Loans held for investment, at fair value | 2007
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Percentage of underlying mortgages, year originated	20.90%	20.90%
Loans held for investment, at fair value | 2008
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Percentage of underlying mortgages, year originated	6.80%	6.50%
Loans held for investment, at fair value | 2009
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Percentage of underlying mortgages, year originated	1.70%	1.50%
Loans held for investment, at fair value | 2010 and later
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Percentage of underlying mortgages, year originated	20.40%	17.30%