XML 123 R106.htm IDEA: XBRL DOCUMENT
v3.19.1

Provisions - Other Benefit Plans (Details) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2018 USD ($) plan | Dec. 31, 2017 USD ($)
Other provisions [abstract] |  |
Provisions for litigation | $ 4,450 | $ 8,900
Litigation paid | $ 4,450 |
Globe Metallurgical Inc [Member] |  |
Other Benefit Plans [Abstract] |  |
Company match percentage | 25.00 |
Globe Metallurgical Inc [Member] | North America |  |
Other Benefit Plans [Abstract] |  |
Number of defined contribution plans provided | plan | 2 |
Maximum | Globe Metallurgical Inc [Member] |  |
Other Benefit Plans [Abstract] |  |
Percentage of compensation | 6.00 |
Asbestos-related claims |  |
Other provisions [abstract] |  |
Bond to guarantee civil financial responsibility | $ 1,775 |

X
- Definition The amount of bond to guarantee civil financial responsibility + References No definition available. + Details
Name: | gsm_BondToGuaranteeCivilFinancialResponsibility
Namespace Prefix: | gsm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Percentage employer matches of the employee's percentage contribution matched. + References No definition available. + Details
Name: | gsm_IfrsDefinedContributionPlanEmployerMatchingContributionPercentOfMatch
Namespace Prefix: | gsm_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | duration

X
- Definition Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan. + References No definition available. + Details
Name: | gsm_IfrsDefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent
Namespace Prefix: | gsm_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the number of defined contribution plans provided. + References No definition available. + Details
Name: | gsm_NumberOfDefinedContributionPlans
Namespace Prefix: | gsm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition n/a + References No definition available. + Details
Name: | gsm_OtherBenefitPlansAbstract
Namespace Prefix: | gsm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The cash outflows for payment of litigation. + References No definition available. + Details
Name: | gsm_PaymentOfLitigation
Namespace Prefix: | gsm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The amount of provisions related to litigation. + References No definition available. + Details
Name: | gsm_ProvisionsForLitigationCurrent
Namespace Prefix: | gsm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Details
Name: | ifrs-full_SignificantInvestmentsInSubsidiariesAxis=gsm_GlobeMetallurgicalIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_GeographicalAreasAxis=srt_NorthAmericaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_RangeAxis=ifrs-full_TopOfRangeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ClassesOfContingentLiabilitiesAxis=gsm_LegalProceedingsAsbestosClaimsContingentLiabilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |