v3.26.1
Acquisition Activity (Fair Value and Unpaid Principal Balance of Loans Acquired) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jan. 05, 2026
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Business Combination [Line Items]          
Acquired gross charge-offs   $ 0 $ 0 $ 45 $ 0
Total commercial lending          
Business Combination [Line Items]          
Acquired gross charge-offs   0 0 10 0
Total consumer lending          
Business Combination [Line Items]          
Acquired gross charge-offs   $ 0 $ 0 35 $ 0
FirstBank Holding Company          
Business Combination [Line Items]          
Net loans $ 15,177        
Acquired gross charge-offs       $ 45  
FirstBank Holding Company | Carrying Amount          
Business Combination [Line Items]          
Net loans 16,170        
Acquired gross charge-offs 45        
FirstBank Holding Company | Fair Value          
Business Combination [Line Items]          
Net loans 15,177        
FirstBank Holding Company | Total commercial lending | Carrying Amount          
Business Combination [Line Items]          
Net loans 8,517        
FirstBank Holding Company | Total commercial lending | Fair Value          
Business Combination [Line Items]          
Net loans 8,000        
FirstBank Holding Company | Total commercial lending | Commercial and industrial | Carrying Amount          
Business Combination [Line Items]          
Net loans 3,354        
FirstBank Holding Company | Total commercial lending | Commercial and industrial | Fair Value          
Business Combination [Line Items]          
Net loans 3,165        
FirstBank Holding Company | Total commercial lending | Commercial real estate | Carrying Amount          
Business Combination [Line Items]          
Net loans 5,163        
FirstBank Holding Company | Total commercial lending | Commercial real estate | Fair Value          
Business Combination [Line Items]          
Net loans 4,835        
FirstBank Holding Company | Total consumer lending | Carrying Amount          
Business Combination [Line Items]          
Net loans 7,653        
FirstBank Holding Company | Total consumer lending | Fair Value          
Business Combination [Line Items]          
Net loans 7,177        
FirstBank Holding Company | Total consumer lending | Residential real estate | Carrying Amount          
Business Combination [Line Items]          
Net loans 7,061        
FirstBank Holding Company | Total consumer lending | Residential real estate | Fair Value          
Business Combination [Line Items]          
Net loans 6,615        
FirstBank Holding Company | Total consumer lending | Home equity | Carrying Amount          
Business Combination [Line Items]          
Net loans 499        
FirstBank Holding Company | Total consumer lending | Home equity | Fair Value          
Business Combination [Line Items]          
Net loans 477        
FirstBank Holding Company | Total consumer lending | Credit card and other consumer | Carrying Amount          
Business Combination [Line Items]          
Net loans 93        
FirstBank Holding Company | Total consumer lending | Credit card and other consumer | Fair Value          
Business Combination [Line Items]          
Net loans $ 85