Revenue from contracts with customers - Contract balances (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Contract asset current	$ 3.0
Contract asset noncurrent	3.3
Receivables	701.8	$ 679.1
Receivables - increase (decrease)	21.2	(45.1)	$ (15.8)
Customer Asset	6.3	0.4
Contract Asset - increase (decrease)	5.9
Contract liability	17.9	15.1
Increase (Decrease) in Accounts Receivable	22.7
Contract Liability - increase (decrease)	2.8
Revenue recognized included in beginning balance	12.5
Capitalized costs to obtain contracts	2.0	0.7
Capitalized costs amortization expense	$ 0.7	$ 0.5

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

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Amount of amortization expense for asset recognized from cost incurred to obtain or fulfill contract with customer.

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Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer.

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Amount of increase (decrease) in revenue recognized for cumulative catch-up adjustment from change in measure of progress which increases (decreases) right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

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Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

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Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as current.

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Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

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Amount of increase (decrease) in revenue recognized for cumulative catch-up adjustment from change in measure of progress which (increases) decreases obligation to transfer good or service to customer for which consideration from customer has been received or is due.

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Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

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The increase (decrease) during the reporting period in amount due within one year (or one business cycle) from customers for the credit sale of goods and services.

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The increase (decrease) during the reporting period in the total amount due within one year (or one operating cycle) from all parties, associated with underlying transactions that are classified as operating activities.

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