XML 44 R31.htm IDEA: XBRL DOCUMENT v3.22.2.2
Allowance for Loan Losses - Allowance for Credit Losses and Recorded Investments in Loans (Parenthetical) (Detail) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2022
Sep. 30, 2021
Sep. 30, 2022
Sep. 30, 2021
Accounts Notes And Loans Receivable [Line Items]        
Adjustment resulting from the change in charge-off rate $ 30 $ 16 $ 30 $ 16
Expected future recoveries of current period defaults 19 6 43 16
Change in balance during period (32) (37) (49) (82)
Sale of private education loan       1,600
Private Education Loans [Member]        
Accounts Notes And Loans Receivable [Line Items]        
Adjustment resulting from the change in charge-off rate 30 16 30 16
Beginning of period expected future recoveries on previously fully charged-off loans 312 434 329 479
Expected future recoveries of current period defaults 19 6 43 16
Recoveries (cash collected) (14) (22) (43) (69)
Charge-offs (as a result of lower recovery expectations) (37) (21) (49) (29)
End of period expected future recoveries on previously fully charged-off loans 280 397 280 397
Change in balance during period (32) (37) $ (49) $ (82)
Private Education Loans [Member] | Loans Receivable For Previously Fully Charged Off Loans [Member]        
Accounts Notes And Loans Receivable [Line Items]        
Adjustment resulting from the change in charge-off rate $ 30 $ 16    
Private Education Loans [Member] | Minimum [Member]        
Accounts Notes And Loans Receivable [Line Items]        
Net charge off rate on defaulted loans 81.70% 81.40%    
Private Education Loans [Member] | MaximumMember        
Accounts Notes And Loans Receivable [Line Items]        
Net charge off rate on defaulted loans 81.90% 81.70%