Credit losses Credit losses (Details)	3 Months Ended
	Mar. 31, 2020 USD ($) country	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
Valuation Allowance [Line Items]
Number of Countries in which Entity Operates | country	100
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for doubtful accounts, beginning balance	$ 30,200,000
Retained earnings	449,900,000		$ 457,400,000
Provision for uncollectible accounts receivable(a)	12,300,000
Write-offs less recoveries	(6,600,000)
Foreign currency exchange effects	(900,000)
Allowance for doubtful accounts, ending balance	37,300,000
Internal Loss AR Rebuild
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for uncollectible accounts receivable(a)	9,400,000
Allowance for doubtful accounts, ending balance	$ 23,000,000.0
Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2016-13
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Retained earnings		$ 2,300,000