Stockholders' equity - Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 1,611.5	$ 1,450.9	$ 1,091.3
Other comprehensive income before reclassifications	20.5	4.0
Amounts reclassified from accumulated other comprehensive income (loss)	(1.3)	5.2
Total other comprehensive income (loss), net of tax	19.2	9.2	(15.8)
Ending balance	1,387.7	1,611.5	1,450.9
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(16.1)	(25.3)	(9.5)
Total other comprehensive income (loss), net of tax	19.2	9.2	(15.8)
Ending balance	3.1	(16.1)	(25.3)
Defined Benefit Pension Plan
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(4.0)	(7.7)
Other comprehensive income before reclassifications	8.7	4.3
Amounts reclassified from accumulated other comprehensive income (loss)	(1.2)	(0.6)
Total other comprehensive income (loss), net of tax	7.5	3.7	(4.3)
Ending balance	3.5	(4.0)	(7.7)
Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(4.5)	(11.0)
Other comprehensive income before reclassifications	10.8	0.7
Amounts reclassified from accumulated other comprehensive income (loss)	(0.1)	5.8
Total other comprehensive income (loss), net of tax	10.7	6.5	(9.4)
Ending balance	6.2	(4.5)	(11.0)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(7.6)	(6.6)
Other comprehensive income before reclassifications	1.0	(1.0)
Amounts reclassified from accumulated other comprehensive income (loss)	0.0	0.0
Total other comprehensive income (loss), net of tax	1.0	(1.0)	(2.1)
Ending balance	$ (6.6)	$ (7.6)	$ (6.6)