v3.25.2
Fair value measurements - Assets and Liabilities Measured at Estimated Fair Value on Recurring Basis (Detail) - USD ($)
Jun. 30, 2025
Dec. 31, 2024
Level 3 | Measurement Input, Commitment Expiration    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Held-for-sale measurement input (as a percent) 0.30 0.06
Recurring | Fair Value Measurements    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Trading account $ 93,000,000 $ 101,000,000
Investment securities available for sale: 21,540,000,000 18,849,000,000
Equity securities 274,000,000 235,000,000
Real estate loans held for sale 583,000,000 521,000,000
Other assets 265,000,000 255,000,000
Total assets 22,755,000,000 19,961,000,000
Other liabilities 554,000,000 822,000,000
Total liabilities 554,000,000 822,000,000
Recurring | Fair Value Measurements | U.S. Treasury    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: 7,837,000,000 7,931,000,000
Recurring | Fair Value Measurements | Commercial    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: 4,767,000,000 3,702,000,000
Recurring | Fair Value Measurements | Residential    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: 8,933,000,000 7,214,000,000
Recurring | Fair Value Measurements | Other    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: 3,000,000 2,000,000
Recurring | Level 1    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Trading account 93,000,000 101,000,000
Investment securities available for sale: 0 0
Equity securities 274,000,000 235,000,000
Real estate loans held for sale 0 0
Other assets 0 0
Total assets 367,000,000 336,000,000
Other liabilities 0 0
Total liabilities 0 0
Recurring | Level 1 | U.S. Treasury    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: 0 0
Recurring | Level 1 | Commercial    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: 0 0
Recurring | Level 1 | Residential    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: 0 0
Recurring | Level 1 | Other    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: 0 0
Recurring | Level 2    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Trading account 0 0
Investment securities available for sale: 21,540,000,000 18,849,000,000
Equity securities 0 0
Real estate loans held for sale 583,000,000 521,000,000
Other assets 260,000,000 251,000,000
Total assets 22,383,000,000 19,621,000,000
Other liabilities 554,000,000 790,000,000
Total liabilities 554,000,000 790,000,000
Recurring | Level 2 | U.S. Treasury    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: 7,837,000,000 7,931,000,000
Recurring | Level 2 | Commercial    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: 4,767,000,000 3,702,000,000
Recurring | Level 2 | Residential    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: 8,933,000,000 7,214,000,000
Recurring | Level 2 | Other    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: 3,000,000 2,000,000
Recurring | Level 3    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Trading account 0 0
Investment securities available for sale: 0 0
Equity securities 0 0
Real estate loans held for sale 0 0
Other assets 5,000,000 4,000,000
Total assets 5,000,000 4,000,000
Other liabilities 0 32,000,000
Total liabilities 0 32,000,000
Recurring | Level 3 | U.S. Treasury    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: 0 0
Recurring | Level 3 | Commercial    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: 0 0
Recurring | Level 3 | Residential    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: 0 0
Recurring | Level 3 | Other    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale: $ 0 $ 0