v3.26.1
Business Combination - Additional Information (Details)
$ / shares in Units, $ in Millions
 3 Months Ended 12 Months Ended
Feb. 01, 2026
USD ($)
banking_center_location
$ / shares
shares
Jan. 30, 2026
$ / shares
Mar. 31, 2026
USD ($)
$ / shares
Dec. 31, 2025
USD ($)
$ / shares
Business Combination [Line Items]        
Preferred stock, liquidation preference per share (in dollars per share) | $ / shares     $ 25,000 $ 25,000
Goodwill acquired | $     $ 5,019 $ 29
Comerica Incorporated        
Business Combination [Line Items]        
Fair value of stock issued | $ $ 12,700      
Full-service banking centers | banking_center_location 351      
Shares issued in business combination (in shares) | shares 240,000,000      
Price per common share (in dollars per share) | $ / shares $ 93.73      
Closing price of stock | $ / shares   $ 50.22    
Goodwill acquired | $ $ 5,000      
Comerica Incorporated | Common Stock        
Business Combination [Line Items]        
Fair value of stock issued | $ $ 12,056      
Shares issued per acquiree share (in shares) | shares 1.8663      
Comerica Incorporated | Depository Shares        
Business Combination [Line Items]        
Shares issued in business combination (in shares) | shares 16,000,000      
Comerica Incorporated | Fair value of preferred stock issued        
Business Combination [Line Items]        
Fair value of stock issued | $ $ 412      
Preferred stock, issued (in shares) | shares 400,000      
Preferred stock, liquidation preference per share (in dollars per share) | $ / shares $ 1,000      
Preferred stock, dividend rate 6.875%      
Comerica Incorporated | Fixed Rate Reset Non-Cumulative Perpetual Stock, Series B | Comerica Incorporated        
Business Combination [Line Items]        
Preferred stock, dividend rate   6.875%    
Comerica Incorporated | Series M Preferred Stock        
Business Combination [Line Items]        
Shares issued per acquiree share (in shares) | shares 1