XML 127 R110.htm IDEA: XBRL DOCUMENT
v3.19.1

Bank borrowings - Borrowing detail by maturity - (Details) $ in Thousands | Dec. 31, 2018 USD ($)
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Borrowings [abstract] |
Non-Current Amount | $ 132,821
Credit facilities |
Borrowings [abstract] |
Non-Current Amount | $ 132,821

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- References No definition available. + Details
Name: | ifrs-full_BorrowingsAbstract
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition The non-current portion of non-current borrowings. [Refer: Borrowings] + 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 + Details
Name: | ifrs-full_LongtermBorrowings
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Details
Name: | ifrs-full_BorrowingsByNameAxis=gsm_CreditFacilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |