Mortgage-Backed Securities - Percentage of Non-Agency RMBS By Year Originated (Details) - Non-Agency RMBS	Sep. 30, 2024	Dec. 31, 2023
Origination Year as a Percentage of Outstanding Principal Balance:
Percentage of underlying mortgages, year originated	100.00%	100.00%
2003 and prior
Origination Year as a Percentage of Outstanding Principal Balance:
Percentage of underlying mortgages, year originated	1.10%	1.20%
2004
Origination Year as a Percentage of Outstanding Principal Balance:
Percentage of underlying mortgages, year originated	1.10%	0.80%
2005
Origination Year as a Percentage of Outstanding Principal Balance:
Percentage of underlying mortgages, year originated	7.40%	8.20%
2006
Origination Year as a Percentage of Outstanding Principal Balance:
Percentage of underlying mortgages, year originated	40.60%	43.30%
2007
Origination Year as a Percentage of Outstanding Principal Balance:
Percentage of underlying mortgages, year originated	27.70%	32.50%
2008 and later
Origination Year as a Percentage of Outstanding Principal Balance:
Percentage of underlying mortgages, year originated	22.10%	14.00%