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Use of Special Purpose Entities and Variable Interest Entities - Loan Securitization Transaction (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2022	Dec. 31, 2021
Variable Interest Entity [Line Items]
Weighted Average Cost of Funding	3.60%	3.60%	2.44%
Asset-backed Securities, Securitized Loans and Receivables
Variable Interest Entity [Line Items]
Aggregate unpaid principal balance of residential whole loans sold	$ 6,497,783	$ 6,497,783	$ 3,984,355
Outstanding amount of Senior Bonds, at carrying value	972,058	972,058	1,334,342
Outstanding amount of Senior Bonds, at fair value	2,860,253	2,860,253	1,316,131
Outstanding amount of Senior Bonds, total	$ 3,832,311	$ 3,832,311	$ 2,650,473
Weighted Average Cost of Funding	3.23%	3.23%	2.01%
Weighted average contractual maturity of Senior Bonds		37 years	36 years
Cash received		$ 5,762,491	$ 3,682,082
Debt issuance cost	$ 3,700	3,700	6,800
Senior Notes
Variable Interest Entity [Line Items]
Cash received	749,500	2,100,000
Senior Notes | Asset-backed Securities, Securitized Loans and Receivables
Variable Interest Entity [Line Items]
Debt instrument, face amount	5,792,100	5,792,100	3,667,790
Proceeds from Senior bond sold with Step up feature		$ 1,800,000	329,000
Senior Notes | Asset-backed Securities, Securitized Loans and Receivables | Minimum
Variable Interest Entity [Line Items]
Debt instrument, basis spread on variable rate		1.00%
Debt instrument, coupon step-up period		30 months
Senior Notes | Asset-backed Securities, Securitized Loans and Receivables | Maximum
Variable Interest Entity [Line Items]
Debt instrument, basis spread on variable rate		3.00%
Debt instrument, coupon step-up period		48 months
Senior Notes | Asset-backed Securities, Securitized Loans and Receivables | Median
Variable Interest Entity [Line Items]
Debt instrument, basis spread on variable rate		2.00%
Senior Support Certificates | Asset-backed Securities, Securitized Loans and Receivables
Variable Interest Entity [Line Items]
Debt instrument, face amount	$ 672,860	$ 672,860	$ 283,930

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