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Supplemental cash flow information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Condensed Cash Flow Statements, Captions [Line Items]
Interest	$ 15.3	$ 7.5
Income taxes, net	11.4	20.5
Financing Leases	12.1	9.5
Restricted cash	97.1		$ 136.1
Cash and cash equivalents	283.2		343.4
Cash, Cash Equivalents, and Restricted Cash	380.3	$ 721.6	479.5	$ 726.9
Cash from Short Term Borrowings
Condensed Cash Flow Statements, Captions [Line Items]
Restricted cash	10.3		10.5
Cash Held From Customers
Condensed Cash Flow Statements, Captions [Line Items]
Restricted cash	51.9		90.3
Deposits liability
Condensed Cash Flow Statements, Captions [Line Items]
Restricted cash	$ 34.9		$ 35.3