v3.26.1
Fair Value Measurements - Assets and Liabilities Recorded as Fair Value on Nonrecurring Basis (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total Gains (Losses) $ (14) $ (13) $ (40) $ (64)  
Consumer loans          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total Gains (Losses) 3 2 3 3  
Commercial loans held for sale          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total Gains (Losses) (2) 0 (1) 0  
Commercial Loans          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total Gains (Losses) (15) $ (15) (42) $ (67)  
Fair Value, Nonrecurring          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis 893   893   $ 1,713
Fair Value, Nonrecurring | Level 1          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis 0   0   0
Fair Value, Nonrecurring | Level 2          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis 551   551   1,371
Fair Value, Nonrecurring | Level 3          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis 342   342   342
Fair Value, Nonrecurring | Consumer loans          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis 91   91   94
Fair Value, Nonrecurring | Consumer loans | Level 1          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis 0   0   0
Fair Value, Nonrecurring | Consumer loans | Level 2          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis 91   91   94
Fair Value, Nonrecurring | Consumer loans | Level 3          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis 0   0   0
Fair Value, Nonrecurring | Commercial loans held for sale          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis 460   460   1,277
Fair Value, Nonrecurring | Commercial loans held for sale | Level 1          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis 0   0   0
Fair Value, Nonrecurring | Commercial loans held for sale | Level 2          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis 460   460   1,277
Fair Value, Nonrecurring | Commercial loans held for sale | Level 3          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis 0   0   0
Fair Value, Nonrecurring | Commercial Loans          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis 342   342   342
Fair Value, Nonrecurring | Commercial Loans | Level 1          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis 0   0   0
Fair Value, Nonrecurring | Commercial Loans | Level 2          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis 0   0   0
Fair Value, Nonrecurring | Commercial Loans | Level 3          
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]          
Total assets at fair value on a non-recurring basis $ 342   $ 342   $ 342