Segment Reporting Assets and Liabilities by Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Total Assets	$ 14,111,525	$ 14,111,525	$ 14,085,886
Liabilities	12,736,762	12,736,762	12,865,000
Total Equity	1,374,763	$ 1,374,763	1,220,886	$ 1,322,938	$ 1,323,556
Investment Portfolio Segment
Segment Reporting Information [Line Items]
Total Assets	5,386,586		5,635,657
Liabilities	4,082,404		4,499,669
Total Equity	1,304,182		1,135,988
Longbridge Segment
Segment Reporting Information [Line Items]
Total Assets	8,557,559
Liabilities	8,390,816
Total Equity	166,743
Corporate and Other
Segment Reporting Information [Line Items]
Total Assets	167,380		222,720
Liabilities	263,542		273,018
Total Equity	$ (96,162)		$ (50,298)