Fair Value - Carrying and Fair Values of Notes Payable Secured by Credit Risk Transfer and Mortgage Servicing Rights and Exchangeable Senior Notes (Detail) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Notes Payable Secured by Credit Risk Transfer and Mortgage Servicing Assets [Member] \| Carrying Value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Notes payable	$ 2,396,545	$ 2,258,128
Notes Payable Secured by Credit Risk Transfer and Mortgage Servicing Assets [Member] \| Fair Value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Notes payable	2,405,192	2,268,438
Unsecured Senior Notes [Member] \| Carrying Value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Notes payable	684,506	1,028,300
Unsecured Senior Notes [Member] \| Fair Value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Notes payable	$ 712,515	$ 1,073,341

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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+ Details