v3.25.2
Fair Value Accounting - Additional Information (Detail)
 6 Months Ended 12 Months Ended
Jun. 30, 2025
USD ($)
Dec. 31, 2024
USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Other assets acquired through foreclosure $ 218,000,000 $ 52,000,000
Fair value 16,898,000,000 13,468,000,000
Commitments and contingencies (Note 15)
U.S. Treasury securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value 5,504,000,000 4,383,000,000
Significant Unobservable Inputs (Level 3)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Impaired loans with an allowance recorded $ 40,000,000 $ 46,000,000
Junior Subordinated Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt Instrument, measurement input 0.0630 0.0743
Percentage of LIBOR 4.29% 4.31%
Period of basis point spread 2.01% 3.12%
Fair Value, Nonrecurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Loans HFI $ 300,000,000 $ 561,000,000
Other assets acquired through foreclosure 218,000,000 52,000,000
Fair Value, Nonrecurring | Letter of Credit | Estimate of Fair Value Measurement    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Commitments and contingencies (Note 15) 0 0
Fair Value, Nonrecurring | Significant Unobservable Inputs (Level 3)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Loans HFI 300,000,000 561,000,000
Other assets acquired through foreclosure 218,000,000 52,000,000
Fair Value, Nonrecurring | Quoted Prices in Active Markets for Identical Assets (Level 1)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Loans HFI 0 0
Other assets acquired through foreclosure 0 0
Fair Value, Nonrecurring | Significant Other Observable Inputs (Level 2)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Loans HFI 0 0
Other assets acquired through foreclosure 0 0
Fair Value, Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value 16,898,000,000 13,468,000,000
Fair Value, Recurring | Estimate of Fair Value Measurement    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value 16,898,000,000 13,468,000,000
Fair Value, Recurring | U.S. Treasury securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value 5,504,000,000 4,383,000,000
Fair Value, Recurring | Significant Unobservable Inputs (Level 3)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value 0 0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Estimate of Fair Value Measurement    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value 0 0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value 0 0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value 5,532,000,000 4,385,000,000
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Estimate of Fair Value Measurement    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value 5,532,000,000 4,385,000,000
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value 5,504,000,000 4,383,000,000
Fair Value, Recurring | Significant Other Observable Inputs (Level 2)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value 11,366,000,000 9,083,000,000
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Estimate of Fair Value Measurement    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value 11,366,000,000 9,083,000,000
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value $ 0 $ 0