v3.26.1
Allowance for Loan Losses - Education Loans - Summary of Performance and Related Loan Status of Loans Modified (Details) - Private Education Loans [Member] - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Accounts Notes And Loans Receivable [Line Items]    
Payment status (Amortized Cost) $ 2,566 $ 2,680
School/Deferment [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Payment status (Amortized Cost) 18 24
Forbearance [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Payment status (Amortized Cost) 94 73
Financing Asset, Not Past Due [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Payment status (Amortized Cost) 1,987 2,056
Financial Asset, 31 to 60 Days Past Due [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Payment status (Amortized Cost) 179 191
Financial Asset, 61 to 90 Days Past Due [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Payment status (Amortized Cost) 113 125
Financial Asset, 90 Days Past Due [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Payment status (Amortized Cost) $ 175 $ 211