v3.25.4
Stock-based compensation - stock option rollforward information (Details) - Common stock including paid-in capital
$ / shares in Units, shares in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2025
USD ($)
$ / shares
shares
Number of options outstanding  
Beginning balance (in shares) | shares 11.9
Granted (in shares) | shares 1.5
Exercised (in shares) | shares (0.1)
Forfeited (in shares) | shares (1.6)
Ending balance (in shares) | shares 11.7
Weighted average exercise price per outstanding option  
Beginning balance (in dollars per share) | $ / shares $ 21.94
Granted (in dollars per share) | $ / shares 16.01
Exercised (in dollars per share) | $ / shares 7.80
Forfeited (in dollars per share) | $ / shares 22.57
Ending balance (in dollars per share) | $ / shares $ 21.18
Other information about options outstanding  
Aggregate intrinsic value | $ $ 0.0
Weighted average remaining contractual term 4 years 2 months 12 days
Information about options expected to vest and exercisable  
Options expected to vest, number | shares 2.0
Options expected to vest, weighted average exercise price per option | $ / shares $ 19.16
Options expected to vest, aggregate intrinsic value | $ $ 0.0
Options expected to vest, weighted average remaining term 8 years 7 months 6 days
Options exercisable, number | shares 9.7
Options exercisable, weighted average exercise price per option | $ / shares $ 21.57
Options exercisable, aggregate intrinsic value | $ $ 0.0
Options exercisable, weighted average remaining term 3 years 4 months 24 days