Supplemental cash flow information (Details) - USD ($) $ in Millions |
9 Months Ended | |||
|---|---|---|---|---|
Sep. 30, 2018 |
Sep. 30, 2017 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Condensed Cash Flow Statements, Captions [Line Items] | ||||
| Interest | $ 38.5 | $ 19.8 | ||
| Income taxes, net | 72.8 | 64.9 | ||
| Capital Leases | 42.0 | 33.4 | ||
| Restricted cash | 92.7 | $ 112.6 | ||
| Cash and cash equivalents | 314.2 | 614.3 | ||
| Cash, Cash Equivalents, and Restricted Cash | 406.9 | $ 327.5 | 726.9 | $ 239.0 |
| Cash from Short Term Borrowings | ||||
| Condensed Cash Flow Statements, Captions [Line Items] | ||||
| Restricted cash | 11.3 | 27.0 | ||
| Cash Held From Customers | ||||
| Condensed Cash Flow Statements, Captions [Line Items] | ||||
| Restricted cash | 46.9 | 74.7 | ||
| Deposits liability | ||||
| Condensed Cash Flow Statements, Captions [Line Items] | ||||
| Restricted cash | $ 34.5 | $ 10.9 | ||