v3.26.1
Business Combinations - Additional Information (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
3 Months Ended 6 Months Ended 30 Months Ended
Apr. 07, 2026
Jun. 30, 2026
Jun. 30, 2026
Jun. 30, 2026
Dec. 31, 2025
Business Combination [Line Items]          
Common stock, par value (in dollars per share)   $ 0.01 $ 0.01 $ 0.01 $ 0.01
Goodwill   $ 31,866 $ 31,866 $ 31,866 $ 28,509
Launch and integration expenses     96    
Discover          
Business Combination [Line Items]          
Business combination, acquisition related costs   298 713 2,100  
Brex Inc.          
Business Combination [Line Items]          
Fair value of purchase consideration $ 4,521        
Fair value of cash consideration transferred $ 2,630        
Number of shares of Capital One treasury stock issued in the acquisition (in shares) 10.6        
Common stock, par value (in dollars per share) $ 0.01        
Business combination, consideration transferred, equity interest, share issued, value $ 1,900        
Preliminary fair value of assets acquired 2,774        
Goodwill 3,069        
Recognized long-term debt 815        
Launch and integration expenses   96      
Brex Inc. | Credit Card          
Business Combination [Line Items]          
Preliminary fair value of assets acquired 5,800        
Goodwill 3,100 $ 2,400 $ 2,400 $ 2,400  
Recognized long-term debt 815        
Cash and cash equivalent $ 725        
Weighted average remaining amortization period 5 years        
Brex Inc. | Minimum | Credit Card          
Business Combination [Line Items]          
Weighted average remaining amortization period 10 years        
Brex Inc. | Maximum | Credit Card          
Business Combination [Line Items]          
Weighted average remaining amortization period 12 years        
Brex Inc. | Technology-Based Intangible Assets          
Business Combination [Line Items]          
Finite lived intangible assets $ 510        
Brex Inc. | Technology-Based Intangible Assets | Credit Card          
Business Combination [Line Items]          
Finite lived intangible assets 510        
Brex Inc. | Purchased credit card relationships          
Business Combination [Line Items]          
Finite lived intangible assets 432        
Brex Inc. | Purchased credit card relationships | Credit Card          
Business Combination [Line Items]          
Finite lived intangible assets $ 432