Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Additional Information (Detail)

v3.20.2
Fair Value Measurements - Additional Information (Detail) - USD ($)
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Ginnie Mae loans subject to repurchase right description     If a borrower makes no payment for three consecutive months, the servicer has the option to repurchase the delinquent loan for an amount equal to 100% of the loan’s remaining principal balance  
Ginnie Mae        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Payments for loans     $ 0  
Percent of remaining principal balance of delinquent loan repurchase option 100.00%   100.00%  
Minimum | Discount Rate        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Range of risk adjusted discount rate 15.00% 8.00% 8.00% 8.00%
Maximum | Discount Rate        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Range of risk adjusted discount rate 20.00% 20.00% 20.00% 20.00%
Median | Discount Rate        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Range of risk adjusted discount rate 20.00% 15.00% 15.00% 15.00%