Segment information - Customer Revenue by Classes of Similar Products or Services (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue from External Customer [Line Items]
Revenue	$ 2,054.4	$ 2,026.3	$ 2,222.8
Operating Segments
Revenue from External Customer [Line Items]
Revenue	1,742.4	1,713.3	1,878.4
Other revenue
Revenue from External Customer [Line Items]
Revenue	313.4	313.1	344.4
Elimination of intercompany revenue
Revenue from External Customer [Line Items]
Revenue	$ (1.4)	$ (0.1)	$ 0.0