Stock-based compensation - expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Other information about options outstanding
Expense	$ 12.5	$ 7.3	$ 36.5	$ 35.1
Equity Award
Other information about options outstanding
Expense	11.9	7.4	36.1	36.2
Stock options
Other information about options outstanding
Expense	2.0	3.0	5.4	7.8
RSUs
Other information about options outstanding
Expense	9.6	4.1	29.9	27.5
Other
Other information about options outstanding
Expense	0.9	0.2	1.2	(0.2)
Liability Award
Other information about options outstanding
Expense	$ 0.6	$ (0.1)	$ 0.4	$ (1.1)