Common stock and additional paid-in capital - Schedule of Stockholders' Equity (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, common shares, outstanding (in shares)			22.2
Beginning balance, equity	$ 243.0	$ 468.5	$ 376.4	$ 501.6
Stock-based compensation - RSUs	0.5	2.8	3.2	5.5
Stock-based compensation - options	$ 0.4	1.1	$ 1.0	1.8
Ending balance, common shares, outstanding (in shares)	22.5		22.5
Ending balance, equity	$ 235.7	$ 439.9	$ 235.7	$ 439.9
Number of common shares
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, common shares, outstanding (in shares)	22.4	22.1	22.2	22.0
Settlement of RSUs (in shares)	0.1		0.3	0.1
Ending balance, common shares, outstanding (in shares)	22.5	22.2	22.5	22.2
Common stock and additional paid-in capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, equity	$ 651.6	$ 638.7	$ 648.3	$ 635.3
Stock-based compensation - RSUs	0.5	2.8	3.2	5.5
Stock-based compensation - options	0.4	1.1	1.0	1.8
Ending balance, equity	$ 652.5	$ 642.2	$ 652.5	$ 642.2