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Residential Whole Loans - Allowance for Credit Losses (Details) - Residential whole loans - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Dec. 31, 2024
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 9,949	$ 10,194	$ 10,665	$ 13,271	$ 19,612	$ 20,451	$ 10,665
Current provision/(reversal)	276	791	145	(1,942)	(1,079)	(460)
Write-offs	(142)	(1,036)	(616)	(672)	(5,262)	(379)
Ending balance	10,083	9,949	10,194	10,657	13,271	19,612	10,083
Non-QM loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	5,122,926						5,122,926	$ 4,291,086
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	2,015	1,928	2,125	1,355	1,681	1,871	2,125
Current provision/(reversal)	205	87	(197)	387	(326)	(190)
Write-offs	(38)	0	0	0	0	0
Ending balance	2,182	2,015	1,928	1,742	1,355	1,681	2,182
Business purpose loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	2,642,818						2,642,818	3,396,181
Business purpose loans \| Single-family rental loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	1,246,595						1,246,595	1,356,400
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	937	980	366	609	4,642	4,355	366
Current provision/(reversal)	(78)	(43)	614	205	978	228
Write-offs	(30)	0	0	(439)	(5,011)
Write-offs						59
Ending balance	829	937	980	375	609	4,642	829
Business purpose loans \| Single-family transitional loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	792,079						792,079	1,100,855
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	512	865	1,389	1,301	1,699	2,587	1,389
Current provision/(reversal)	548	669	(88)	48	(317)	(472)
Write-offs	0	(1,022)	(436)	(181)	(81)	(416)
Ending balance	1,060	512	865	1,168	1,301	1,699	1,060
Business purpose loans \| Single-family transitional loans \| Collateral Dependent Methodology
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	3,800			18,900			3,800
Legacy RPL/NPL loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	1,006,236						1,006,236	$ 1,082,549
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	6,485	6,421	6,785	10,006	11,590	11,638	6,785
Current provision/(reversal)	(399)	78	(184)	(2,582)	(1,414)	(26)
Write-offs	(74)	(14)	(180)	(52)	(170)	(22)
Ending balance	6,012	$ 6,485	$ 6,421	7,372	$ 10,006	$ 11,590	6,012
Legacy RPL/NPL loans \| Collateral Dependent Methodology
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	$ 32,100			$ 39,300			$ 32,100