Segment financial information - reconciliation of segment profitability measure (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Reconciliation of Adjusted EBITDA from net income or loss
Net income	$ 164.0	$ 47.0
Interest expense	51.5	94.5
Income tax expense	47.4	17.7
Depreciation and amortization	89.0	96.5
Loss on extinguishment of debt	5.2	0.0
Net foreign currency loss from financing activities	0.8	1.6
Other stock-based compensation expense (benefit)	0.6	(1.1)
Restructuring and severance charges	1.6	1.2
Transaction related expenses and other	3.0	1.8
Integration and planning expenses	0.0	3.6
Adjusted EBITDA	$ 363.1	$ 262.8