v3.26.1
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
 3 Months Ended 12 Months Ended
Mar. 31, 2026
USD ($)
UsdPerLoan
Dec. 31, 2025
USD ($)
UsdPerLoan
Mar. 31, 2025
USD ($)
Dec. 31, 2024
USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Balance at end of period $ 3,623,979 $ 3,644,702 $ 3,770,034 $ 3,867,394
Unpaid principal balance of underlying loans, Fair Value $ 212,198,589 $ 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 3.90% 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 $ (49,635) $ (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 (97,738) (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 (152,590) (118,218)    
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 (39,505) (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 (78,085) (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 (63,164) (63,918)    
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 (15,791) (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 (31,582) (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 $ (189,634) $ (233,683)    
Minimum [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Estimated fair value inputs, Option-adjusted spread 3.20% 3.60%    
Estimated fair value inputs, Prepayment speed 7.00% 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) 2 years 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 6.40% 6.20%    
Estimated fair value inputs, Prepayment speed 25.60% 21.50%    
Estimated fair value inputs, Annual per-loan cost of servicing | UsdPerLoan 94 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) 8 years 10 months 24 days 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 7.20% 8.40%    
Estimated fair value inputs, Option-adjusted spread 4.60% 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 6 months 7 years 8 months 12 days