Financial risk management - Foreign currency risk (Details) - Currency risk - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Disclosure of financial instruments by type of interest rate [line items]
Net working capital asset	$ 104.4	$ 85.3
Reasonably possible change in risk variable, percent	10.00%
Impact on value of net working capital	$ 10.4	$ 8.5

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

No definition available.

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- Definition

The amount of risk exposure associated with financial instruments with a shared characteristic that identifies a concentration of risks. [Refer: Financial instruments, class [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2017-01-01
-Paragraph B8
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-01&anchor=para_B8_c&doctype=Appendix&seq=2
-URIDate 2017-03-09

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- Definition

Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Change In Risk Variable, Impact On Equity

+ References

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- Definition

Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Change In Risk Variable, Percent

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