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Financial risk management - interest-bearing financial liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of financial instruments by type of interest rate [line items]
Obligations under finance leases	$ 66,471	$ 82,633
Debt instruments	352,594	350,270
Other financial liabilities	32,788	49,011
Additional borrowing cost if 1% increase in floating interest rate	1,425	161
Interest rate risk
Disclosure of financial instruments by type of interest rate [line items]
Bank borrowings	141,012	1,003
Obligations under finance leases	66,471	82,633
Debt instruments	352,595	350,270
Other financial liabilities	61,849	99,391
Interest-bearing financial liabilities	$ 621,927	$ 533,297
Percentage of exposure to floating interest rate	31.00%	83.00%
Increase in floating interest rate, Percentage	1.00%
Interest rate risk | Fixed rate
Disclosure of financial instruments by type of interest rate [line items]
Debt instruments	$ 352,595	$ 350,270
Other financial liabilities	61,849	86,238
Interest-bearing financial liabilities	414,444	436,508
Interest rate risk | Floating rate
Disclosure of financial instruments by type of interest rate [line items]
Bank borrowings	141,012	1,003
Obligations under finance leases	66,471	82,633
Other financial liabilities		13,153
Interest-bearing financial liabilities	$ 207,483	$ 96,789

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- Definition

The amount of change in borrowing cost due to one percent change in floating interest borrowing rate.

+ References

No definition available.

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- Definition

Represents borrowings and other financial liabilities.

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- Definition

The percentage of sensitive analysis of floating interest rate of borrowings.

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- Definition

The amount of interest bearing financial liabilities.

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No definition available.

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- Definition

Percentage of exposure to floating interest rate.

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No definition available.

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- Definition

The amount of instruments issued by the entity that represent indebtedness.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 55
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_55&doctype=Standard
-URIDate 2018-03-16

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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.

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- Definition

The amount of liabilities related to the entity's leases. Lease is a contract, or part of a contract, that conveys the right to use an underlying asset for a period of time in exchange for consideration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2019-01-01
-Name IFRS
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-IssueDate 2018-01-01
-Paragraph 47
-Subparagraph b
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-URIDate 2018-03-16

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- Definition

The amount of non-current financial liabilities that the entity does not separately disclose in the same statement or note. [Refer: Other financial liabilities]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph B13
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B13_c&doctype=Appendix&seq=2
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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