Annual report pursuant to Section 13 and 15(d)

Concentrations of Risk - Summary of Percentage of Reverse Mortgage Loans (Detail)

v3.22.0.1
Concentrations of Risk - Summary of Percentage of Reverse Mortgage Loans (Detail) - Credit Concentration Risk - Reverse Mortgage - Mortgage Loans Benchmark - Mortgage Loans Customer
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Schedule Of Percentage Of Reverse Mortgage Loans [Line Items]    
Concentration Risk, Percentage 100.00% 100.00%
Agency    
Schedule Of Percentage Of Reverse Mortgage Loans [Line Items]    
Concentration Risk, Percentage 70.00% 72.00%
Non-Agency    
Schedule Of Percentage Of Reverse Mortgage Loans [Line Items]    
Concentration Risk, Percentage 30.00% 28.00%