Quarterly report pursuant to Section 13 or 15(d)

Fair Value - Summary of Fair Value and Unpaid Principal Balance ("UPB") of Financial Assets and Liabilities With Elected Fair Value Option (Details)

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Fair Value - Summary of Fair Value and Unpaid Principal Balance ("UPB") of Financial Assets and Liabilities With Elected Fair Value Option (Details) - USD ($)
$ in Thousands
Mar. 31, 2024
Dec. 31, 2023
Estimated Fair Value    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Assets at fair value under the fair value option $ 18,050,772 $ 17,548,763
Estimated Fair Value | Loans held for investment | Reverse mortgage loans    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Assets at fair value under the fair value option 535,159 574,271
Estimated Fair Value | Loans held for investment | Commercial mortgage loans    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Assets at fair value under the fair value option 751 957
Estimated Fair Value | Loans held for sale | Loans held for sale - residential mortgage loans    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Assets at fair value under the fair value option 2,465 4,246
Estimated Fair Value | HMBS related obligations    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Liabilities at fair value under the fair value option 17,827,060 17,353,720
Estimated Fair Value | Nonrecourse debt in consolidated VIE trusts and reverse loan financing liability    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Liabilities at fair value under the fair value option 7,883,472 7,876,932
Estimated Fair Value | Nonrecourse commercial loan financing liability    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Liabilities at fair value under the fair value option 14,424 27,268
Estimated Fair Value | Reverse mortgage loans | Loans held for investment, subject to nonrecourse debt:    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Assets at fair value under the fair value option 8,327,915 8,138,403
Estimated Fair Value | Commercial mortgage loans | Loans held for investment, subject to nonrecourse debt:    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Assets at fair value under the fair value option 79,687 133,990
Unpaid Principal Balance    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Assets at fair value under the fair value option 17,113,496 16,875,437
Unpaid Principal Balance | Loans held for investment | Reverse mortgage loans    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Assets at fair value under the fair value option 519,237 558,577
Unpaid Principal Balance | Loans held for investment | Commercial mortgage loans    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Assets at fair value under the fair value option 1,044 1,044
Unpaid Principal Balance | Loans held for sale | Loans held for sale - residential mortgage loans    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Assets at fair value under the fair value option 6,997 9,247
Unpaid Principal Balance | HMBS related obligations    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Liabilities at fair value under the fair value option 17,113,496 16,875,437
Unpaid Principal Balance | Nonrecourse debt in consolidated VIE trusts and reverse loan financing liability    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Liabilities at fair value under the fair value option 8,447,617 8,429,135
Unpaid Principal Balance | Nonrecourse commercial loan financing liability    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Liabilities at fair value under the fair value option 22,295 26,661
Unpaid Principal Balance | Reverse mortgage loans | Loans held for investment, subject to nonrecourse debt:    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Assets at fair value under the fair value option 8,483,961 8,257,750
Unpaid Principal Balance | Commercial mortgage loans | Loans held for investment, subject to nonrecourse debt:    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Assets at fair value under the fair value option $ 92,561 $ 136,622