Quarterly report pursuant to Section 13 or 15(d)

Fair Value - Summary of Non-Agency Reverse Mortgage Loans (Detail)

v3.21.2
Fair Value - Summary of Non-Agency Reverse Mortgage Loans (Detail) - Non Agency Reverse Mortgage Loans [Member]
9 Months Ended 12 Months Ended
Sep. 30, 2021
Dec. 31, 2020
Minimum [Member] | Loan to value [Member]    
Fair Value Non Agency Reverse Mortgage Loans Classified As Reverse Mortgage Loans Held For Investment Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Loan to value 7.40% 0.10%
Minimum [Member] | Home price appreciation [Member]    
Fair Value Non Agency Reverse Mortgage Loans Classified As Reverse Mortgage Loans Held For Investment Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Home price appreciation 3.40% 1.10%
Maximum [Member] | Loan to value [Member]    
Fair Value Non Agency Reverse Mortgage Loans Classified As Reverse Mortgage Loans Held For Investment Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Loan to value 68.30% 62.10%
Maximum [Member] | Home price appreciation [Member]    
Fair Value Non Agency Reverse Mortgage Loans Classified As Reverse Mortgage Loans Held For Investment Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Home price appreciation 9.60% 8.90%
Weighted Average [Member] | Weighted average remaining life in years [Member]    
Fair Value Non Agency Reverse Mortgage Loans Classified As Reverse Mortgage Loans Held For Investment Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Weighted-average remaining life in years 7 years 9 months 18 days 8 years
Weighted Average [Member] | Loan to value [Member]    
Fair Value Non Agency Reverse Mortgage Loans Classified As Reverse Mortgage Loans Held For Investment Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Loan to value 47.90% 44.00%
Weighted Average [Member] | Conditional repayment rate [Member]    
Fair Value Non Agency Reverse Mortgage Loans Classified As Reverse Mortgage Loans Held For Investment Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Conditional repayment rate 16.50% 16.80%
Weighted Average [Member] | Loss severity [Member]    
Fair Value Non Agency Reverse Mortgage Loans Classified As Reverse Mortgage Loans Held For Investment Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Loss severity 10.00% 10.00%
Weighted Average [Member] | Home price appreciation [Member]    
Fair Value Non Agency Reverse Mortgage Loans Classified As Reverse Mortgage Loans Held For Investment Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Home price appreciation 4.70% 5.50%
Weighted Average [Member] | Discount rate [Member]    
Fair Value Non Agency Reverse Mortgage Loans Classified As Reverse Mortgage Loans Held For Investment Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Discount rate 3.40% 3.60%