v3.26.1
Fair Value - Summary of Changes in Fair Value Included in Current Period Results of Operations (Detail) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Credit Risk Transfer Strips [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) $ 10,361 $ (2,048)
Credit Risk Transfer Strips [Member] | Net Loan Servicing Fees [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Credit Risk Transfer Strips [Member] | Net Gains on Loans Held for Sale [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Credit Risk Transfer Strips [Member] | Net (Losses) Gains on Investments and Financings [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 10,361 (2,048)
Credit Risk Transfer Strips [Member] | Net Interest Expense [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Interest-only security payable [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 3,418 (1,732)
Interest-only security payable [Member] | Net Loan Servicing Fees [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Interest-only security payable [Member] | Net Gains on Loans Held for Sale [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Interest-only security payable [Member] | Net (Losses) Gains on Investments and Financings [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 3,418 (1,732)
Interest-only security payable [Member] | Net Interest Expense [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Asset-backed financings of VIEs [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 66,167 (28,055)
Asset-backed financings of VIEs [Member] | Net Loan Servicing Fees [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Asset-backed financings of VIEs [Member] | Net Gains on Loans Held for Sale [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Asset-backed financings of VIEs [Member] | Net (Losses) Gains on Investments and Financings [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 62,236 (29,423)
Asset-backed financings of VIEs [Member] | Net Interest Expense [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 3,931 1,368
Liabilities, Total [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 69,585 (29,787)
Liabilities, Total [Member] | Net Loan Servicing Fees [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Liabilities, Total [Member] | Net Gains on Loans Held for Sale [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Liabilities, Total [Member] | Net (Losses) Gains on Investments and Financings [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 65,654 (31,155)
Liabilities, Total [Member] | Net Interest Expense [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 3,931 1,368
Mortgage Backed Securities [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) (25,007) 74,925
Mortgage Backed Securities [Member] | Net Loan Servicing Fees [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Mortgage Backed Securities [Member] | Net Gains on Loans Held for Sale [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Mortgage Backed Securities [Member] | Net (Losses) Gains on Investments and Financings [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) (33,407) 64,855
Mortgage Backed Securities [Member] | Net Interest Expense [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 8,400 10,070
Loans held for sale [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) (419) 46,511
Loans held for sale [Member] | Net Loan Servicing Fees [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Loans held for sale [Member] | Net Gains on Loans Held for Sale [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) (419) 46,511
Loans held for sale [Member] | Net (Losses) Gains on Investments and Financings [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Loans held for sale [Member] | Net Interest Expense [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Loans held for investment [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) (75,027) 27,994
Loans held for investment [Member] | Net Loan Servicing Fees [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Loans held for investment [Member] | Net Gains on Loans Held for Sale [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Loans held for investment [Member] | Net (Losses) Gains on Investments and Financings [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) (65,803) 28,681
Loans held for investment [Member] | Net Interest Expense [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) (9,224) (687)
Mortgage servicing rights [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) (61,299) (144,590)
Mortgage servicing rights [Member] | Net Loan Servicing Fees [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) (61,299) (144,590)
Mortgage servicing rights [Member] | Net Gains on Loans Held for Sale [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Mortgage servicing rights [Member] | Net (Losses) Gains on Investments and Financings [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Mortgage servicing rights [Member] | Net Interest Expense [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) 0 0
Assets, Total [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) (151,391) 2,792
Assets, Total [Member] | Net Loan Servicing Fees [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) (61,299) (144,590)
Assets, Total [Member] | Net Gains on Loans Held for Sale [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) (419) 46,511
Assets, Total [Member] | Net (Losses) Gains on Investments and Financings [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) (88,849) 91,488
Assets, Total [Member] | Net Interest Expense [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value included in current period income (expense) $ (824) $ 9,383