Income taxes - Total Income (Loss) From Continuing Operations Before Income Taxes and Provision (Benefit) for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income (loss) from continuing operations before income taxes
United States	$ (443.5)	$ (316.3)	$ (148.4)
Foreign	(18.2)	44.5	87.8
Loss from continuing operations before income taxes	(461.7)	(271.8)	(60.6)
Current
United States	9.1	7.3	(17.7)
Foreign	38.1	51.5	41.0
Total	47.2	58.8	23.3
Deferred
Foreign	(59.1)	(13.4)	4.4
Total (benefit) provision for income taxes	$ (11.9)	$ 45.4	$ 27.7

Amount of current federal tax expense (benefit) attributable to income (loss) from continuing operations. Includes, but is not limited to, current national tax expense (benefit) for non-US (United States of America) jurisdiction.

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The portion of earnings or loss from continuing operations before income taxes that is attributable to domestic operations.

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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The portion of earnings or loss from continuing operations before income taxes that is attributable to foreign operations, which is defined as Income or Loss generated from operations located outside the entity's country of domicile.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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