v3.26.3
Fair Value - Quantitative Summary of Key Assumptions Used in Valuation of MSRs as of Dates Presented, and Effect on Estimated Fair Value from Adverse Changes in Those Inputs (Detail)
$ in Thousands
 9 Months Ended 12 Months Ended
Sep. 30, 2026
USD ($)
UsdPerLoan
Dec. 31, 2025
USD ($)
UsdPerLoan
Jun. 30, 2026
USD ($)
Sep. 30, 2025
USD ($)
 [1]
Jun. 30, 2025
USD ($)
Dec. 31, 2024
USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Balance at end of period $ 3,513,760 [1] $ 3,644,702 $ 3,575,603 $ 3,668,755 $ 3,739,106 $ 3,867,394
Unpaid principal balance of underlying loans, Fair Value $ 192,136,463 $ 215,781,639        
Weighted-average annual servicing fee rate (in basis points), Fair value input 28.00% 28.00%        
Weighted-average note interest rate, Fair value 3.80% 3.90%        
Pricing Spread [Member] | Effect On Value Of Five Percentage Adverse Change            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Effect on value of percentage adverse change, Fair value input $ (39,462) $ (61,563)        
Pricing Spread [Member] | Effect On Value Of Ten Percentage Adverse Change            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Effect on value of percentage adverse change, Fair value input (78,145) (120,960)        
Pricing Spread [Member] | Effect On Value Of Twenty Percentage Adverse Change            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Effect on value of percentage adverse change, Fair value input (152,834) (233,683)        
Prepayment Speed [Member] | Effect On Value Of Five Percentage Adverse Change            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Effect on value of percentage adverse change, Fair value input (33,437) (30,295)        
Prepayment Speed [Member] | Effect On Value Of Ten Percentage Adverse Change            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Effect on value of percentage adverse change, Fair value input (66,364) (60,089)        
Prepayment Speed [Member] | Effect On Value Of Twenty Percentage Adverse Change            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Effect on value of percentage adverse change, Fair value input (130,368) (118,218)        
Cost of Servicing [Member] | Effect On Value Of Five Percentage Adverse Change            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Effect on value of percentage adverse change, Fair value input (14,053) (15,979)        
Cost of Servicing [Member] | Effect On Value Of Ten Percentage Adverse Change            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Effect on value of percentage adverse change, Fair value input (28,107) (31,959)        
Cost of Servicing [Member] | Effect On Value Of Twenty Percentage Adverse Change            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Effect on value of percentage adverse change, Fair value input $ (56,213) $ (63,918)        
Minimum [Member]            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Estimated fair value inputs, Option-adjusted spread 2.70% 3.60%        
Estimated fair value inputs, Prepayment speed 5.90% 7.00%        
Estimated fair value inputs, Annual per-loan cost of servicing | UsdPerLoan 69 68        
Minimum [Member] | Mortgage service rights [Member]            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Estimated fair value inputs, Life (in years) 1 year 10 months 24 days 2 years 1 month 6 days        
Maximum [Member]            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Estimated fair value inputs, Option-adjusted spread 5.90% 6.20%        
Estimated fair value inputs, Prepayment speed 24.40% 21.50%        
Estimated fair value inputs, Annual per-loan cost of servicing | UsdPerLoan 107 90        
Maximum [Member] | Mortgage service rights [Member]            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Estimated fair value inputs, Life (in years) 10 years 6 months 7 years 10 months 24 days        
Weighted Average [Member]            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Estimated fair value inputs, Pricing spread 6.10% 8.40%        
Estimated fair value inputs, Option-adjusted spread 4.50% 3.60%        
Estimated fair value inputs, Annual per-loan cost of servicing | UsdPerLoan 69 68        
Weighted Average [Member] | Mortgage service rights [Member]            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Estimated fair value inputs, Life (in years) 8 years 10 months 24 days 7 years 8 months 12 days        
[1] During the third quarter of 2026, the Company entered into an agreement to sell a portfolio of Agency MSRs with an aggregate UPB of approximately $10.0 billion. The transaction is expected to close in the fourth quarter of 2026.