Income taxes - Components of the Provisions for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Current
Federal	$ (9.4)	$ (3.1)	$ 64.6
State	1.9	14.9	28.4
International	33.8	28.9	16.5
Total current	26.3	40.7	109.5
Deferred
Federal	(37.7)	37.1	0.5
State	(3.2)	4.2	0.1
International	7.2	1.6	(3.9)
Total deferred	(33.7)	43.0	(3.4)
Income tax (benefit) provision	$ (7.4)	$ 83.7	$ 106.1