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Supplemental cash flow information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Condensed Cash Flow Statements, Captions [Line Items]
Interest	$ 56.0	$ 38.5
Income taxes, net	33.4	72.8
Financing Leases	46.2	42.0
Restricted cash	89.2		$ 136.1
Cash and cash equivalents	337.0		343.4
Cash, Cash Equivalents, and Restricted Cash	426.2	$ 406.9	479.5	$ 726.9
Cash from Short Term Borrowings
Condensed Cash Flow Statements, Captions [Line Items]
Restricted cash	10.0		10.5
Cash Held From Customers
Condensed Cash Flow Statements, Captions [Line Items]
Restricted cash	38.5		90.3
Deposits liability
Condensed Cash Flow Statements, Captions [Line Items]
Restricted cash	$ 40.7		$ 35.3