v3.26.1
Fair value of financial instruments - Carrying Value and Estimated Fair Value of Financial Liabilities (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Aug. 31, 2023
Jul. 31, 2023
$700 million senior bond | Senior Notes        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Debt instrument, face amount $ 700      
$575 million secured bond (Level 1) | Secured Debt        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Debt instrument, face amount 575   $ 75 $ 500
Level 1 | Fair value | $700 million senior bond | Senior Notes        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Debt 677 $ 0    
Level 1 | Fair value | $575 million secured bond (Level 1) | Secured Debt        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Debt 0 598    
Level 1 | Carrying value | $700 million senior bond | Senior Notes        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Debt 687 0    
Level 1 | Carrying value | $575 million secured bond (Level 1) | Secured Debt        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Debt 0 563    
Level 3 | Fair value | Unsecured senior convertible bond | Secured Debt        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Debt 55 56    
Level 3 | Carrying value | Unsecured senior convertible bond | Secured Debt        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Debt $ 50 $ 50