Quarterly report pursuant to Section 13 or 15(d)

Fair Value - Summary of Fix & Flip - Securitized Commercial Mortgage Loans (Detail)

v3.21.2
Fair Value - Summary of Fix & Flip - Securitized Commercial Mortgage Loans (Detail) - Fix Flip Securitized Commercial Mortgage Loans [Member]
 9 Months Ended 12 Months Ended
Sep. 30, 2021
Dec. 31, 2020
Minimum [Member] | Discount rate [Member]    
Fair Value Fix And Flip Mortgage Loan Securitized Held For Investment Subject To Nonrecourse Debt Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Discount rate   6.70%
Minimum [Member] | Loss frequency [Member]    
Fair Value Fix And Flip Mortgage Loan Securitized Held For Investment Subject To Nonrecourse Debt Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Loss frequency 0.30% 0.20%
Maximum [Member] | Discount rate [Member]    
Fair Value Fix And Flip Mortgage Loan Securitized Held For Investment Subject To Nonrecourse Debt Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Discount rate   10.00%
Maximum [Member] | Loss frequency [Member]    
Fair Value Fix And Flip Mortgage Loan Securitized Held For Investment Subject To Nonrecourse Debt Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Loss frequency 74.30% 44.00%
Weighted Average [Member] | Prepayment Rate [Member]    
Fair Value Fix And Flip Mortgage Loan Securitized Held For Investment Subject To Nonrecourse Debt Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Prepayment rate (SMM) 14.30% 17.10%
Weighted Average [Member] | Discount rate [Member]    
Fair Value Fix And Flip Mortgage Loan Securitized Held For Investment Subject To Nonrecourse Debt Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Discount rate 5.20% 6.70%
Weighted Average [Member] | Loss frequency [Member]    
Fair Value Fix And Flip Mortgage Loan Securitized Held For Investment Subject To Nonrecourse Debt Measured On Recurring And Nonrecurring Basis Fair Value Measurement [Line Items]    
Loss frequency 0.50% 0.60%