v3.26.1
Shareholders' equity - Issued and Outstanding Preferred Stock (Detail) - USD ($)
$ / shares in Units, $ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Class of Stock [Line Items]          
Preferred stock, shares issued (in shares) 10,220,000   10,220,000   10,260,000
Preferred stock, shares outstanding (in shares) 10,220,000   10,220,000   10,260,000
Carrying Amount $ 2,434   $ 2,434   $ 2,834
Preferred Series F          
Class of Stock [Line Items]          
Preferred stock, shares issued (in shares) 50,000   50,000   50,000
Preferred stock, shares outstanding (in shares) 50,000   50,000   50,000
Preferred stock, liquidation preference per share (in USD per share) $ 10,000   $ 10,000    
Preferred stock dividend rate (as a percent)     5.125%    
Carrying Amount $ 500   $ 500   $ 500
Preferred stock per share dividend amount (in USD per share) $ 128.13 $ 128.13 $ 256.25 $ 256.25  
Preferred stock. dividend rate spread (as a percent)     3.78%    
Preferred Series G          
Class of Stock [Line Items]          
Preferred stock, shares issued (in shares) 0   0   40,000
Preferred stock, shares outstanding (in shares) 0   0   40,000
Preferred stock, liquidation preference per share (in USD per share) $ 10,000   $ 10,000    
Preferred stock dividend rate (as a percent)     0.00%    
Carrying Amount $ 0   $ 0   $ 400
Preferred stock per share dividend amount (in USD per share) $ 0 182.60 $ 182.60 365.20  
Preferred Series H          
Class of Stock [Line Items]          
Preferred stock, shares issued (in shares) 10,000,000   10,000,000   10,000,000
Preferred stock, shares outstanding (in shares) 10,000,000   10,000,000   10,000,000
Preferred stock, liquidation preference per share (in USD per share) $ 25   $ 25    
Preferred stock dividend rate (as a percent)     5.625%    
Carrying Amount $ 261   $ 261   $ 261
Preferred stock per share dividend amount (in USD per share) $ 0.35 0.35 $ 0.70 0.70  
Preferred stock. dividend rate spread (as a percent)     4.28%    
Preferred Series I          
Class of Stock [Line Items]          
Preferred stock, shares issued (in shares) 50,000   50,000   50,000
Preferred stock, shares outstanding (in shares) 50,000   50,000   50,000
Preferred stock, liquidation preference per share (in USD per share) $ 10,000   $ 10,000    
Preferred stock dividend rate (as a percent)     3.50%    
Carrying Amount $ 500   $ 500   $ 500
Preferred stock per share dividend amount (in USD per share) $ 87.50 87.50 $ 175.00 175.00  
Preferred stock. dividend rate spread (as a percent)     2.679%    
Preferred Series J          
Class of Stock [Line Items]          
Preferred stock, shares issued (in shares) 75,000   75,000   75,000
Preferred stock, shares outstanding (in shares) 75,000   75,000   75,000
Preferred stock, liquidation preference per share (in USD per share) $ 10,000   $ 10,000    
Preferred stock dividend rate (as a percent)     7.50%    
Carrying Amount $ 733   $ 733   $ 733
Preferred stock per share dividend amount (in USD per share) $ 187.50 187.50 $ 375.00 375.00  
Preferred Series K          
Class of Stock [Line Items]          
Preferred stock, shares issued (in shares) 45,000   45,000   45,000
Preferred stock, shares outstanding (in shares) 45,000   45,000   45,000
Preferred stock, liquidation preference per share (in USD per share) $ 10,000   $ 10,000    
Preferred stock dividend rate (as a percent)     6.35%    
Carrying Amount $ 440   $ 440   $ 440
Preferred stock per share dividend amount (in USD per share) $ 158.75 $ 0 $ 317.50 $ 0