v3.26.1
Allowance for Loan Losses - Education Loans - Amortized Cost Basis of Loans Modified to Borrowers with Financial Difficulty (Parenthetical) (Details) - Private Education Loans [Member] - USD ($)
$ in Millions
Jun. 30, 2026
Jun. 30, 2025
Accounts Notes And Loans Receivable [Line Items]    
Loans $ 15,146 $ 15,530
Interest Rate Concession [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Loans $ 1,000 $ 1,000