v3.25.2
Fair Value - Summary of Key Unobservable Inputs Used in Valuation Credit Risk Transfer Strip Liabilities (Detail) - Credit Risk Transfer Strips [Member] - USD ($)
$ in Thousands
Jun. 30, 2025
Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of CRT derivatives liabilities $ 10,479 $ 4,060
Unpaid principal balance of loans in the reference pools $ 15,624,260 $ 16,287,660
Maximum [Member] | Discount Rate [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in valuation 8.80% 9.10%
Maximum [Member] | Voluntary Prepayment Speed [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in valuation 7.50% 7.50%
Maximum [Member] | Involuntary Prepayment Speed [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in valuation 0.30% 0.30%
Maximum [Member] | Remaining Loss Expectation [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in valuation 1.50% 1.50%
Minimum [Member] | Discount Rate [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in valuation 6.10% 7.10%
Minimum [Member] | Voluntary Prepayment Speed [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in valuation 6.90% 6.90%
Minimum [Member] | Involuntary Prepayment Speed [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in valuation 0.10% 0.10%
Minimum [Member] | Remaining Loss Expectation [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in valuation 0.40% 0.40%
Weighted Average [Member] | Discount Rate [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in valuation 8.40% 8.80%
Weighted Average [Member] | Voluntary Prepayment Speed [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in valuation 7.00% 7.00%
Weighted Average [Member] | Involuntary Prepayment Speed [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in valuation 0.10% 0.10%
Weighted Average [Member] | Remaining Loss Expectation [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in valuation 0.50% 0.50%