v3.26.1
Stockholders' equity - Accumulated Other Comprehensive Loss (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Accumulated other comprehensive income (loss) (net of tax and noncontrolling interest):        
Balance at beginning of period     $ 1,023.2  
Balance at end of period $ 1,044.2   1,044.2  
Marketable Securities        
Accumulated other comprehensive income (loss) (net of tax and noncontrolling interest):        
Balance at beginning of period 1.7 $ 1.7 1.7 $ 1.7
Balance at end of period 1.7 1.7 1.7 1.7
Currency Translation        
Accumulated other comprehensive income (loss) (net of tax and noncontrolling interest):        
Balance at beginning of period (87.4) (100.3) (90.1) (111.7)
Other comprehensive income (loss) arising during the period (2.8) 9.5 (0.1) 20.9
Balance at end of period (90.2) (90.8) (90.2) (90.8)
Accumulated Defined Benefit Plans Adjustment | Defined Benefit Pension Plans        
Accumulated other comprehensive income (loss) (net of tax and noncontrolling interest):        
Balance at beginning of period (17.5) (48.9) (17.7) (49.4)
Other comprehensive income (loss) arising during the period 0.3 0.4 0.5 0.9
Balance at end of period (17.2) (48.5) (17.2) (48.5)
Accumulated Defined Benefit Plans Adjustment | OPEB        
Accumulated other comprehensive income (loss) (net of tax and noncontrolling interest):        
Balance at beginning of period 0.3 0.1 0.3 0.2
Other comprehensive income (loss) arising during the period (0.1)   (0.1) (0.1)
Balance at end of period 0.2 0.1 0.2 0.1
Total Accumulated Other Comprehensive Loss        
Accumulated other comprehensive income (loss) (net of tax and noncontrolling interest):        
Balance at beginning of period (102.9) (147.4) (105.8) (159.2)
Other comprehensive income (loss) arising during the period (2.6) 9.9 0.3 21.7
Balance at end of period $ (105.5) $ (137.5) $ (105.5) $ (137.5)