v3.26.3
Fair Value Measurements - Change in Balance Sheet Carrying Value Associated with Level 3 Financial Instruments Carried at Fair Value on Recurring Basis (Detail) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Total gains/(losses):        
Included in earnings $ 14 $ (10) $ (15) $ 142
Fair Value, Net Derivative Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Gain (Loss) on Derivative Instruments, Net, Pretax Gain (Loss) on Derivative Instruments, Net, Pretax Gain (Loss) on Derivative Instruments, Net, Pretax Gain (Loss) on Derivative Instruments, Net, Pretax
Interest Rate Swaps [Member]        
Fair Value Net Derivative Asset Liability Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]        
Balance, beginning of period $ 0 $ 0 $ 0 $ 0
Total gains/(losses):        
Included in earnings 0 0 0 0
Purchases 0 0 0 0
Settlements 0 0 0 0
Other changes 0 0 0 0
Transfers in and/or out of level 3 0 0 0 0
Balance, end of period 0 0 0 0
Change in mark-to-market gains/(losses) relating to instruments still held at the reporting date 0 0 0 0
Cross-Currency Interest Rate Swaps [Member]        
Fair Value Net Derivative Asset Liability Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]        
Balance, beginning of period (91) (75) (76) (244)
Total gains/(losses):        
Included in earnings (9) (10) (38) 142
Purchases 0 0 0 0
Settlements 5 9 19 26
Other changes 0 0 0 0
Transfers in and/or out of level 3 0 0 0 0
Balance, end of period (95) (76) (95) (76)
Change in mark-to-market gains/(losses) relating to instruments still held at the reporting date (4) $ (1) (26) $ 168
Private Education Loans [Member]        
Fair Value Net Derivative Asset Liability Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]        
Balance, beginning of period (0)   0  
Total gains/(losses):        
Included in earnings 11   11  
Purchases 226   226  
Settlements (2)   (2)  
Other changes 0   0  
Transfers in and/or out of level 3 0   0  
Balance, end of period 235   235  
Change in mark-to-market gains/(losses) relating to instruments still held at the reporting date 11   11  
Private Education Loans Commitments [Member]        
Fair Value Net Derivative Asset Liability Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]        
Balance, beginning of period 0   0  
Total gains/(losses):        
Included in earnings 12   12  
Purchases 0   0  
Settlements 0   0  
Other changes 0   0  
Transfers in and/or out of level 3 0   0  
Balance, end of period 12   12  
Change in mark-to-market gains/(losses) relating to instruments still held at the reporting date $ 12   $ 12