Quarterly report pursuant to Section 13 or 15(d)

Fair Value - Summary of Inventory Buyouts (Detail)

v3.21.2
Fair Value - Summary of Inventory Buyouts (Detail) - Inventory Buyouts [Member] - Weighted Average [Member]
 9 Months Ended 12 Months Ended
Sep. 30, 2021
Dec. 31, 2020
Conditional repayment rate [Member]    
Fair Value Inventory Buyouts Classified As Reverse Mortgage Loans Held For Investment Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Conditional repayment rate 44.00% 44.00%
Loss frequency [Member]    
Fair Value Inventory Buyouts Classified As Reverse Mortgage Loans Held For Investment Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Loss frequency 59.10% 46.90%
Loss severity [Member]    
Fair Value Inventory Buyouts Classified As Reverse Mortgage Loans Held For Investment Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Loss severity 5.50% 10.50%
Discount rate [Member]    
Fair Value Inventory Buyouts Classified As Reverse Mortgage Loans Held For Investment Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Discount rate 3.60% 4.10%