v3.26.1
Fair Value Measurements - Carrying Value and Estimated Fair Value of Financial Instruments (Detail) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Jun. 30, 2025
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Federal funds sold and securities purchased under agreements to resell $ 4,457 $ 9,252  
Securities held-to-maturity, net of allowance for credit losses 20,489 18,293  
Loans, net of allowance for credit losses 61,680 59,452 $ 63,585
Commercial loans held for sale 1,305 1,925  
Deposits 126,813 124,097 $ 126,181
Long-term debt 25,305 23,026  
Level 1      
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Short-term financial assets, net of allowance for credit losses 800 800  
Federal funds sold and securities purchased under agreements to resell 0 0  
Securities held-to-maturity, net of allowance for credit losses 5,900 2,800  
Short-term financial liabilities 0 0  
Deposits 0 0  
Long-term debt 0 0  
Level 1 | Commercial loans      
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Loans, net of allowance for credit losses 0 0  
Commercial loans held for sale 0 0  
Level 1 | Consumer loans      
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Loans, net of allowance for credit losses 0 0  
Level 2      
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Short-term financial assets, net of allowance for credit losses 23,900 23,100  
Federal funds sold and securities purchased under agreements to resell 4,500 9,300  
Securities held-to-maturity, net of allowance for credit losses 14,200 15,300  
Short-term financial liabilities 9,100 7,300  
Deposits 123,000 120,500  
Long-term debt 17,000 15,100  
Level 2 | Commercial loans      
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Loans, net of allowance for credit losses 0 0  
Commercial loans held for sale 500 1,300  
Level 2 | Consumer loans      
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Loans, net of allowance for credit losses 0 0  
Level 3      
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Short-term financial assets, net of allowance for credit losses 0 0  
Federal funds sold and securities purchased under agreements to resell 0 0  
Securities held-to-maturity, net of allowance for credit losses 0 0  
Short-term financial liabilities 0 0  
Deposits 0 0  
Long-term debt 0 0  
Level 3 | Commercial loans      
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Loans, net of allowance for credit losses 41,900 39,700  
Commercial loans held for sale 0 0  
Level 3 | Consumer loans      
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Loans, net of allowance for credit losses 19,500 19,800  
Carrying Value      
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Short-term financial assets, net of allowance for credit losses 24,700 23,900  
Federal funds sold and securities purchased under agreements to resell 4,500 9,300  
Securities held-to-maturity, net of allowance for credit losses 20,500 18,300  
Short-term financial liabilities 9,100 7,300  
Deposits 123,100 120,500  
Long-term debt 16,600 14,800  
Carrying Value | Commercial loans      
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Loans, net of allowance for credit losses 41,300 38,900  
Commercial loans held for sale 500 1,300  
Carrying Value | Consumer loans      
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Loans, net of allowance for credit losses 20,400 20,500  
Fair Value      
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Short-term financial assets, net of allowance for credit losses 24,700 23,900  
Federal funds sold and securities purchased under agreements to resell 4,500 9,300  
Securities held-to-maturity, net of allowance for credit losses 20,100 18,100  
Short-term financial liabilities 9,100 7,300  
Deposits 123,000 120,500  
Long-term debt 17,000 15,100  
Fair Value | Commercial loans      
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Loans, net of allowance for credit losses 41,900 39,700  
Commercial loans held for sale 500 1,300  
Fair Value | Consumer loans      
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]      
Loans, net of allowance for credit losses $ 19,500 $ 19,800