Mortgage-Backed Securities - Percentage of Non-Agency RMBS By Year Originated (Details) - Non-Agency RMBS	Mar. 31, 2024	Dec. 31, 2023
Origination Year as a Percentage of Outstanding Principal Balance:
2003 and prior	1.10%	1.20%
2004	0.70%	0.80%
2005	7.80%	8.20%
2006	42.10%	43.30%
2007	31.30%	32.50%
2008 and later	17.00%	14.00%
Total	100.00%	100.00%