v3.25.2
Fair Value - Quantitative Summary of Key Unobservable Inputs Used in Review and Approval of Broker-provided Fair Values for CRT Derivatives (Detail) - CRT Derivatives [Member] - USD ($)
$ in Thousands
 6 Months Ended 12 Months Ended
Jun. 30, 2025
Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value $ 31,147 $ 29,377
UPB of loans in reference pools $ 4,731,905 $ 4,961,644
Discount Rate [Member] | Minimum [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in fair value for CRT agreements 8.70% 9.00%
Discount Rate [Member] | Maximum [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in fair value for CRT agreements 18.70% 11.40%
Discount Rate [Member] | Weighted Average [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in fair value for CRT agreements 8.90% 9.30%
Voluntary Prepayment Speed [Member] | Minimum [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in fair value for CRT agreements 6.80% 7.00%
Voluntary Prepayment Speed [Member] | Maximum [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in fair value for CRT agreements 8.30% 7.60%
Voluntary Prepayment Speed [Member] | Weighted Average [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in fair value for CRT agreements 7.20% 7.30%
Involuntary Prepayment Speed [Member] | Minimum [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in fair value for CRT agreements 0.10% 0.10%
Involuntary Prepayment Speed [Member] | Maximum [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in fair value for CRT agreements 0.30% 0.20%
Involuntary Prepayment Speed [Member] | Weighted Average [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in fair value for CRT agreements 0.10% 0.10%
Measurement Input, Loss Severity | Minimum [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in fair value for CRT agreements 0.00% 0.00%
Measurement Input, Loss Severity | Maximum [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in fair value for CRT agreements 0.10% 0.20%
Measurement Input, Loss Severity | Weighted Average [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Key inputs used in fair value for CRT agreements 0.10% 0.10%